Processing biomass

ABSTRACT

Biomass (e.g., plant biomass, animal biomass, and municipal waste biomass) is processed to produce useful products, such as fuels. For example, systems are described that can use feedstock materials, such as cellulosic and/or lignocellulosic materials, to produce ethanol and/or butanol, e.g., by fermentation.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a Continuation of PCT/US2007/022719, filed Oct. 26,2007, which claimed priority from U.S. Provisional Application Ser. No.60/854,519, filed on Oct. 26, 2006, U.S. Provisional Application Ser.No. 60/863,290, filed on Oct. 27, 2006, U.S. Provisional ApplicationSer. No. 60/859,911, filed on Nov. 17, 2006, U.S. ProvisionalApplication Ser. No. 60/875,144, filed on Dec. 15, 2006, and U.S.Provisional Application Ser. No. 60/881,891, filed on Jan. 23, 2007. Theentirety of each of these applications is incorporated herein byreference.

TECHNICAL FIELD

This invention relates to processing biomass, and products madetherefrom.

BACKGROUND

Cellulosic and lignocellulosic materials, e.g., in fibrous form, areproduced, processed, and used in large quantities in a number ofapplications. Often such materials are used once, and then discarded aswaste, or are simply considered to be waste materials, e.g., sewage,bagasse, sawdust, and stover.

Various cellulosic and lignocellulosic materials, their uses, andapplications have been described in U.S. Pat. Nos. 7,074,918, 6,448,307,6,258,876, 6,207,729, 5,973,035 and 5,952,105; and in various patentapplications, including “FIBROUS MATERIALS AND COMPOSITES,”PCT/US2006/010648, filed on Mar. 23, 2006, AND “FIBROUS MATERIALS ANDCOMPOSITES,” U.S. Patent Application Publication No. 2007/0045456.

SUMMARY

Generally, this invention relates to carbohydrate-containing materials(e.g., biomass materials or biomass-derived materials), methods ofmaking and processing such materials to change their structure, andproducts made from the structurally changed materials. For example, manyof the methods described herein can provide cellulosic and/orlignocellulosic materials that have a lower molecular weight and/orcrystallinity relative to a native material. Many of the methods providematerials that can be more readily utilized by a variety ofmicroorganisms to produce useful products, such as hydrogen, alcohols(e.g., ethanol or butanol), organic acids (e.g., acetic acid),hydrocarbons, co-products (e.g., proteins) or mixtures of any of these.

In one aspect, the invention features a method of changing a molecularstructure of a biomass feedstock, the method comprising converting atreated biomass feedstock to a product, utilizing a microorganism, thetreated biomass feedstock having been prepared by treating a biomassfeedstock having a bulk density of less than about 0.5 g/cm³ using atreatment method selected from the group consisting of radiation,sonication, pyrolysis, and oxidation.

In another aspect, the invention features a method of changing amolecular structure of a biomass feedstock, the method comprisingconverting a treated biomass feedstock to a product, utilizing amicroorganism, the treated biomass feedstock having been prepared bytreating a biomass feedstock having a BET surface area greater thanabout 0.1 m²/g using a treatment methods selected from the groupconsisting of radiation, sonication, pyrolysis, and oxidation.

In a further aspect, the invention features a method of changing amolecular structure of a biomass feedstock, the method comprisingconverting a treated biomass feedstock to a product, utilizing amicroorganism, the treated biomass feedstock having been prepared bytreating a biomass feedstock having a porosity greater than about 50%using one or more treatment methods selected from the group consistingof radiation, sonication, pyrolysis, and oxidation.

Some embodiments of the aspects described above include one or more ofthe following features.

The biomass feedstock can have a bulk density of less than about 0.35g/cm³. The biomass feedstock can have a BET surface area of greater than0.25 m²/g. The biomass feedstock can have a length to diameter ratio ofat least 5. The biomass feedstock can have a porosity greater than 70%.

The method can further include preparing the biomass feedstock byphysically treating an initial feedstock to reduce the bulk density ofthe initial feedstock, e.g., by shearing. The initial feedstock canhave, prior to preparing, a bulk density of greater than about 0.7g/cm³. Reducing the size of the initial feedstock can include stonegrinding, mechanical ripping or tearing, pin grinding, or air attritionmilling. In some cases, the biomass feedstock has internal fibers, andwherein the biomass feedstock has been sheared to an extent that itsinternal fibers are substantially exposed.

In some cases, treating comprises irradiating with an electron beam.Treating can be conducted under conditions selected to reduce themolecular weight of the biomass. Ionizing radiation can be applied tothe biomass feedstock at a total dosage of at least about 5 MRad.Treating can be performed under conditions that are selected to decreaseeither one or both of an average molecular weight and averagecrystallinity of the biomass or increase either one or both of surfacearea and porosity of the biomass.

The biomass feedstock can include a cellulosic or lignocellulosicmaterial. For example, the biomass feedstock can be selected from thegroup consisting of paper, paper products, paper waste, wood, particleboard, sawdust, agricultural waste, sewage, silage, grasses, rice hulls,bagasse, cotton, jute, hemp, flax, bamboo, sisal, abaca, straw, corncobs, corn stover, switchgrass, alfalfa, hay, rice hulls, coconut hair,cotton, seaweed, algae, and mixtures thereof.

Converting can include fermentation. The method can further includesubjecting the treated biomass feedstock to enzymatic hydrolysis. Insome cases, first the treated biomass feedstock is hydrolyzed and thenthe resulting hydrolysis product is converted utilizing themicroorganism. The product can be, for example, a combustible fuel.

In yet another aspect, the invention features a method of making anirradiated wood product, the method comprising irradiating a woodproduct comprising a first carbohydrate-containing material having afirst molecular weight to provide an irradiated wood product comprisinga second carbohydrate-containing material having a second molecularweight higher than the first molecular weight.

Some implementations include one or more of the following features. Theirradiated wood product can comprise lumber, a wood laminate or plywood.The wood product can receive a dose of radiation of from about 0.2 Mradto about 10 Mrad, e.g., from about 0.5 Mrad to about 7.5 Mrad.Irradiating may comprise utilizing a gamma radiation source, and/orelectron beam radiation.

The invention also features an irradiated wood product comprising lumberhaving a molecular weight that is relatively higher than the naturallyoccurring molecular weight of the wood from which the lumber was formed.

In another aspect, the invention features a method comprising convertinga treated biomass feedstock to a product, utilizing a microorganism, thetreated biomass feedstock having been prepared by treating a shearedbiomass feedstock using one or more treatment methods selected from thegroup consisting of radiation, sonication, pyrolysis, and oxidation.

The invention also features a composition comprising a cellulosic orlignocellulosic material having a peak maximum molecular weight of lessthan about 25,000, and a crystallinity of less than about 55 percent.

In some implementations, the material can have a BET surface areagreater than about 0.25 m²/g, e.g., greater than 1 m²/g. The materialcan also have a bulk density of less than about 0.5 g/cm³, and/or alength to diameter ratio of at least 5. In some cases, the material hasa porosity of greater than 70%. The composition may further include anenzyme or microorganism. The material may be sterile. The material mayhave a crystallinity index of about 10 to 50 percent.

The invention also features a method for dissolving a cellulosic orlignocellulosic material, the method comprising combining a cellulosicor lignocellulosic material with a solvent comprising DMAc and a salt.

The salt may comprise a lithium salt, for example a salt selected fromthe group consisting of lithium chloride and lithium carbonate. Themethod may further include irradiating the cellulosic or lignocellulosicmaterial. The cellulosic or lignocellulosic material can be selectedfrom the group consisting of paper, paper products, paper waste, wood,particle board, sawdust, agricultural waste, sewage, silage, grasses,rice hulls, bagasse, cotton, jute, hemp, flax, bamboo, sisal, abaca,straw, corn cobs, corn stover, switchgrass, alfalfa, hay, rice hulls,coconut hair, cotton, seaweed, algae, and mixtures thereof. In somecases the cellulosic or lignocellulosic material has a bulk density ofless than about 0.5 g/cm3 and a porosity of at least 50%.

Examples of microorganisms that may be used to produce useful productsinclude bacteria, yeasts, or combinations thereof. For example, themicroorganism can be a bacterium, e.g., a cellulolytic bacterium, afungus, e.g., a yeast, a plant or a protist, e.g., an algae, a protozoaor a fungus-like protist, e.g., a slime mold.

Examples of products that may be produced include mono-andpolyfunctional C1-C6 alkyl alcohols, mono-and poly-functional carboxylicacids, C1-C6 hydrocarbons, and combinations thereof. Specific examplesof suitable alcohols include methanol, ethanol, propanol, isopropanol,butanol, ethylene glycol, propylene glycol, 1,4-butane diol, glycerin,and combinations thereof. Specific example of suitable carboxylic acidsinclude formic acid, acetic acid, propionic acid, butyric acid, valericacid, caproic acid, palmitic acid, stearic acid, oxalic acid, malonicacid, succinic acid, glutaric acid, oleic acid, linoleic acid, glycolicacid, lactic acid, γ-hydroxybutyric acid, and combinations thereof.Examples of suitable hydrocarbons include methane, ethane, propane,pentane, n-hexane, and combinations thereof. Many of these products maybe used as fuels.

The term “fibrous material,” as used herein, is a material that includesnumerous loose, discrete and separable fibers. For example, a fibrousmaterial can be prepared from a bleached Kraft paper fiber source byshearing, e.g., with a rotary knife cutter.

The term “screen,” as used herein, means a member capable of sievingmaterial according to size. Examples of screens include a perforatedplate, cylinder or the like, or a wire mesh or cloth fabric.

The term “pyrolysis,” as used herein, means to break bonds in a materialby the application of heat energy. Pyrolysis can occur while the subjectmaterial is under vacuum, or immersed in a gaseous material, such as anoxidizing gas, e.g., air or oxygen, or a reducing gas, such as hydrogen.

Oxygen content is measured by elemental analysis by pyrolyzing a samplein a furnace operating at 1300° C. or above.

The term “biomass” refers to any non-fossilized organic matter. Thevarious types of biomass include cellulosic and lignocellulosicmaterials such as plant biomass (defined below), animal biomass (anyanimal by-product, animal waste, etc.) and municipal waste biomass(residential and light commercial refuse with recyclables such as metaland glass removed).

The terms “plant biomass” and “lignocellulosic biomass” refer tovirtually any plant-derived organic matter (woody or non-woody). Plantbiomass can include, but is not limited to, agricultural crop wastes andresidues such as corn stover, wheat straw, rice straw, sugar canebagasse, and the like. Plant biomass further includes, but is notlimited to, trees, woody energy crops, wood wastes and residues such assoftwood forest thinnings, barky wastes, sawdust, paper and pulpindustry waste streams, wood fiber, and the like. Additionally grasscrops, such as switchgrass and the like have potential to be produced ona large-scale as another plant biomass source. For urban areas, the bestpotential plant biomass feedstock includes yard waste (e.g., grassclippings, leaves, tree clippings, and brush) and vegetable processingwaste.

“Lignocellulosic biomass,” is any type of plant biomass such as, but notlimited to, non-woody plant biomass; cultivated crops; grasses, e.g., C4grasses, such as switchgrass, cord grass, rye grass, miscanthus, reedcanary grass, or a combination thereof; sugar processing residues suchas bagasse or beet pulp; agricultural residues, for example, soybeanstover, corn stover, rice straw, rice hulls, barley straw, corn cobs,wheat straw, canola straw, rice straw, oat straw, oat hulls, corn fiber;wood materials such as recycled wood pulp fiber, sawdust, hardwood, forexample aspen wood and sawdust, and softwood; or a combination thereof.Further, the lignocellulosic biomass may include cellulosic wastematerial such as, but not limited to, newsprint, cardboard, sawdust, andthe like.

Lignocellulosic biomass may include one species of fiber or a mixture offibers that originate from different lignocellulosic feedstocks.Furthermore, the lignocellulosic biomass may comprise a freshlignocellulosic feedstock, partially dried lignocellulosic feedstock,fully dried lignocellulosic feedstock or a combination thereof.

For the purposes of this disclosure, carbohydrates are materials thatare composed entirely of one or more saccharide units or that includeone or more saccharide units. Carbohydrates can be polymeric (e.g.,equal to or greater than 10-mer, 100-mer, 1,000-mer, 10,000-mer, or100,000-mer), oligomeric (e.g., equal to or greater than a 4-mer, 5-mer,6-mer, 7-mer, 8-mer, 9-mer or 10-mer), trimeric, dimeric, or monomeric.When the carbohydrates are formed of more than a single repeat unit,each repeat unit can be the same or different.

Examples of polymeric carbohydrates include cellulose, xylan, pectin,and starch, while cellobiose and lactose are examples of dimericcarbohydrates. Examples of monomeric carbohydrates include glucose andxylose.

Carbohydrates can be part of a supramolecular structure, e.g.,covalently bonded into the structure. Examples of such materials includelignocellulosic materials, such as those found in wood.

A combustible fuel is a material capable of burning in the presence ofoxygen. Examples of combustible fuels include ethanol, n-propanol,n-butanol, hydrogen and mixtures of any two or more of these.

Swelling agents as used herein are materials that cause a discernableswelling, e.g., a 2.5 percent increase in volume over an unswollen stateof cellulosic and/or lignocellulosic materials, when applied to suchmaterials as a solution, e.g., a water solution. Examples includealkaline substances, such as sodium hydroxide, potassium hydroxide,lithium hydroxide and ammonium hydroxides, acidifying agents, such asmineral acids (e.g., sulfuric acid, hydrochloric acid and phosphoricacid), salts, such as zinc chloride, calcium carbonate, sodiumcarbonate, benzyltrimethylammonium sulfate, and basic organic amines,such as ethylene diamine.

A “sheared material,” as used herein, is a material that includesdiscrete fibers in which at least about 50% of the discrete fibers havea length/diameter (L/D) ratio of at least about 5, and that has anuncompressed bulk density of less than about 0.6 g/cm³. A shearedmaterial is thus different from a material that has been cut, chopped orground.

Changing a molecular structure of a biomass feedstock, as used herein,means to change the chemical bonding arrangement or conformation of thestructure. For example, the change in the molecular structure caninclude changing the supramolecular structure of the material, oxidationof the material, changing an average molecular weight, changing anaverage crystallinity, changing a surface area, changing a degree ofpolymerization, changing a porosity, changing a degree of branching,grafting on other materials, changing a crystalline domain size, or anchanging an overall domain size.

Unless otherwise defined, all technical and scientific terms used hereinhave the same meaning as commonly understood by one of ordinary skill inthe art to which this invention belongs. Although methods and materialssimilar or equivalent to those described herein can be used in thepractice or testing of the present invention, suitable methods andmaterials are described below. All publications, patent applications,patents, and other references mentioned herein are incorporated byreference in their entirety. In case of conflict, the presentspecification, including definitions, will control. In addition, thematerials, methods, and examples are illustrative only and not intendedto be limiting.

Other features and advantages of the invention will be apparent from thefollowing detailed description, and from the claims.

DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating conversion of biomass intoproducts and co-products.

FIG. 2 is block diagram illustrating conversion of a fiber source into afirst and second fibrous material.

FIG. 3 is a cross-sectional view of a rotary knife cutter.

FIG. 4 is block diagram illustrating conversion of a fiber source into afirst, second and third fibrous material.

FIG. 5 is block diagram illustrating densification of a material.

FIG. 6 is a perspective view of a pellet mill.

FIG. 7A is a densified fibrous material in pellet form.

FIG. 7B is a transverse cross-section of a hollow pellet in which acenter of the hollow is in-line with a center of the pellet.

FIG. 7C is a transverse cross-section of a hollow pellet in which acenter of the hollow is out of line with the center of the pellet.

FIG. 7D is a transverse cross-section of a tri-lobal pellet.

FIG. 8 is a block diagram illustrating a treatment sequence forprocessing feedstock.

FIG. 9 is a perspective, cut-away view of a gamma irradiator.

FIG. 10 is an enlarged perspective view of region R of FIG. 9.

FIG. 11 is a block diagram illustrating an electron beam irradiationfeedstock pretreatment sequence.

FIG. 12 is a schematic view of a system for sonicating a process streamof cellulosic material in a liquid medium.

FIG. 13 is a schematic view of a sonicator having two transducerscoupled to a single horn.

FIG. 14 is a block diagram illustrating a pyrolytic feedstockpretreatment system.

FIG. 15 is a cross-sectional side view of a pyrolysis chamber.

FIG. 16 is a cross-sectional side view of a pyrolysis chamber.

FIG. 17 is a cross-sectional side view of a pyrolyzer that includes aheated filament.

FIG. 18 is a schematic cross-sectional side view of a Curie-Pointpyrolyzer.

FIG. 19 is a schematic cross-sectional side view of a furnace pyrolyzer.

FIG. 20 is a schematic cross-sectional top view of a laser pyrolysisapparatus.

FIG. 21 is a schematic cross-sectional top view of a tungsten filamentflash pyrolyzer.

FIG. 22 is a block diagram illustrating an oxidative feedstockpretreatment system.

FIG. 23 is block diagram illustrating a general overview of the processof converting a fiber source into a product, e.g., ethanol.

FIG. 24 is a cross-sectional view of a steam explosion apparatus.

FIG. 25 is a schematic cross-sectional side view of a hybrid electronbeam/sonication device.

FIG. 26 is a scanning electron micrograph of a fibrous material producedfrom polycoated paper at 25× magnification. The fibrous material wasproduced on a rotary knife cutter utilizing a screen with ⅛ inchopenings.

FIG. 27 is a scanning electron micrograph of a fibrous material producedfrom bleached Kraft board paper at 25× magnification. The fibrousmaterial was produced on a rotary knife cutter utilizing a screen with ⅛inch openings.

FIG. 28 is a scanning electron micrograph of a fibrous material producedfrom bleached Kraft board paper at 25× magnification. The fibrousmaterial was twice sheared on a rotary knife cutter utilizing a screenwith 1/16 inch openings during each shearing.

FIG. 29 is a scanning electron micrograph of a fibrous material producedfrom bleached Kraft board paper at 25× magnification. The fibrousmaterial was thrice sheared on a rotary knife cutter. During the firstshearing, a ⅛ inch screen was used; during the second shearing, a 1/16inch screen was used, and during the third shearing a 1/32 inch screenwas used.

FIG. 30 is a schematic side view of a sonication apparatus, while FIG.31 is a cross-sectional view through the processing cell of FIG. 30.

FIG. 32 is a scanning electron micrograph at 1000× magnification of afibrous material produced from shearing switchgrass on a rotary knifecutter, and then passing the sheared material through a 1/32 inchscreen.

FIGS. 33 and 34 are scanning electron micrographs of the fibrousmaterial of FIG. 32 after irradiation with 10 Mrad and 100 Mrad gammarays, respectively, at 1000× magnification.

FIG. 35 is a scanning electron micrographs of the fibrous material ofFIG. 32 after irradiation with 10 Mrad and sonication at 1000×magnification.

FIG. 36 is a scanning electron micrographs of the fibrous material ofFIG. 32 after irradiation with 100 Mrad and sonication at 1000×magnification.

FIG. 37 is an infrared spectrum of Kraft board paper sheared on a rotaryknife cutter.

FIG. 38 is an infrared spectrum of the Kraft paper of FIG. 37 afterirradiation with 100 Mrad of gamma radiation.

FIG. 39 is a schematic view of a process for biomass conversion.

FIG. 40 is schematic view of another process for biomass conversion.

DETAILED DESCRIPTION

Biomass (e.g., plant biomass, animal biomass, and municipal wastebiomass) can be processed to produce useful products such as fuels.Systems and processes are described below that can use as feedstockmaterials cellulosic and/or lignocellulosic materials that are readilyavailable, but can be difficult to process by processes such asfermentation. Feedstock materials are first physically prepared forprocessing, often by size reduction of raw feedstock materials.Physically prepared feedstock can be pretreated or processed using oneor more of radiation, sonication, oxidation, pyrolysis, and steamexplosion. The various pretreatment systems and methods can be used incombinations of two, three, or even four of these technologies.

In some cases, feedstocks that include one or more saccharide units aretreated to provide materials that include a carbohydrate, such ascellulose, that can be converted by a microorganism to a number ofdesirable products, such as a combustible fuels (e.g., ethanol, butanolor hydrogen). Other products and co-products that can be producedinclude, for example, human food, animal feed, pharmaceuticals, andnutriceuticals.

Types of Biomass

Generally, any biomass material that is or includes carbohydratescomposed entirely of one or more saccharide units or that includes oneor more saccharide units can be processed by any of the methodsdescribed herein. For example, the biomass material can include one ormore cellulosic or lignocellulosic materials.

For example, such materials can include paper, paper products, wood,wood-related materials, particle board, grasses, rice hulls, bagasse,cotton, jute, hemp, flax, bamboo, sisal, abaca, straw, corn cobs, ricehulls, coconut hair, algae, seaweed, cotton, synthetic celluloses, ormixtures of any of these.

Fiber sources include cellulosic fiber sources, including paper andpaper products (e.g., polycoated paper and Kraft paper), andlignocellulosic fiber sources, including wood, and wood-relatedmaterials, e.g., particle board. Other suitable fiber sources includenatural fiber sources, e.g., grasses, rice hulls, bagasse, cotton, jute,hemp, flax, bamboo, sisal, abaca, straw, corn cobs, rice hulls, coconuthair; fiber sources high in α-cellulose content, e.g., cotton; andsynthetic fiber sources, e.g., extruded yarn (oriented yarn orun-oriented yarn). Natural or synthetic fiber sources can be obtainedfrom virgin scrap textile materials, e.g., remnants, or they can be postconsumer waste, e.g., rags. When paper products are used as fibersources, they can be virgin materials, e.g., scrap virgin materials, orthey can be post-consumer waste. Aside from virgin raw materials,post-consumer, industrial (e.g., offal), and processing waste (e.g.,effluent from paper processing) can also be used as fiber sources. Also,the fiber source can be obtained or derived from human (e.g., sewage),animal or plant wastes. Additional fiber sources have been described inU.S. Pat. Nos. 6,448,307, 6,258,876, 6,207,729, 5,973,035 and 5,952,105.

In some embodiments, the carbohydrate is or includes a material havingone or more β-1,4-linkages and having a number average molecular weightbetween about 3,000 and 50,000. Such a carbohydrate is or includescellulose (I), which is derived from (β-glucose 1) through condensationof β(1→4)-glycosidic bonds. This linkage contrasts itself with that forα(1→4)-glycosidic bonds present in starch and other carbohydrates.

Blends of any of the above materials may also be used.

Systems for Treating Biomass

FIG. 1 shows a system 100 for converting biomass, particularly biomasswith significant cellulosic and lignocellulosic components, into usefulproducts and co-products. System 100 includes a feed preparationsubsystem 110, a pretreatment subsystem 114, a primary process subsystem118, and a post-processing subsystem 122. Feed preparation subsystem 110receives biomass in its raw form, physically prepares the biomass foruse as feedstock by downstream processes (e.g., reduces the size of andhomogenizes the biomass), and stores the biomass both in its raw andfeedstock forms. Biomass feedstock with significant cellulosic andlignocellulosic components can have a high average molecular weight andcrystallinity that can make processing the feedstock into usefulproducts (e.g., fermenting the feedstock to produce ethanol) difficult.

Pretreatment subsystem 114 receives feedstock from the feed preparationsubsystem 110 and prepares the feedstock for use in primary productionprocesses by, for example, reducing the average molecular weight andcrystallinity of the feedstock. Primary process subsystem 118 receivespretreated feedstock from pretreatment subsystem 114 and produces usefulproducts (e.g., ethanol, other alcohols, pharmaceuticals, and/or foodproducts). In some cases, the output of primary process subsystem 118 isdirectly useful but, in other cases, requires further processingprovided by post-processing subsystem 122. Post-processing subsystem 122provides further processing to product streams from primary processsystem 118 which require it (e.g., distillation and denaturation ofethanol) as well as treatment for waste streams from the othersubsystems. In some cases, the co-products of subsystems 114, 118, 122can also be directly or indirectly useful as secondary products and/orin increasing the overall efficiency of system 100. For example,post-processing subsystem 122 can produce treated water to be recycledfor use as process water in other subsystems and/or can produce burnablewaste which can be used as fuel for boilers producing steam and/orelectricity.

The optimum size for biomass conversion plants is affected by factorsincluding economies of scale and the type and availability of biomassused as feedstock. Increasing plant size tends to increase economies ofscale associated with plant processes. However, increasing plant sizealso tends to increase the costs (e.g., transportation costs) per unitof feedstock. Studies analyzing these factors suggest that theappropriate size for biomass conversion plants can range from 2000 to10,000 dried tons of feedstock per day depending at least in part on thetype of feedstock used. The type of feedstock can also impact plantstorage requirements with plants designed primarily for processingfeedstock whose availability varies seasonally (e.g., corn stover)requiring more on-or of-site feedstock storage than plants designed toprocess feedstock whose availability is relatively steady (e.g., wastepaper).

Physical Preparation

In some cases, methods of processing begin with a physical preparationof the feedstock, e.g., size reduction of raw feedstock materials, suchas by cutting, grinding, shearing or chopping. In some cases, loosefeedstock (e.g., recycled paper or switchgrass) is prepared by shearingor shredding. Screens and/or magnets can be used to remove oversized orundesirable objects such as, for example, rocks or nails from the feedstream.

Feed preparation systems can be configured to produce feed streams withspecific characteristics such as, for example, specific maximum sizes,specific length-to-width, or specific surface areas ratios. As a part offeed preparation, the bulk density of feedstocks can be controlled(e.g., increased).

Size Reduction

In some embodiments, the material to be processed is in the form of afibrous material that includes fibers provided by shearing a fibersource. For example, the shearing can be performed with a rotary knifecutter.

For example, and by reference to FIG. 2, a fiber source 210 is sheared,e.g., in a rotary knife cutter, to provide a first fibrous material 212.The first fibrous material 212 is passed through a first screen 214having an average opening size of 1.59 mm or less ( 1/16 inch, 0.0625inch) to provide a second fibrous material 216. If desired, fiber sourcecan be cut prior to the shearing, e.g., with a shredder. For example,when a paper is used as the fiber source, the paper can be first cutinto strips that are, e.g., ¼-to ½-inch wide, using a shredder, e.g., acounter-rotating screw shredder, such as those manufactured by Munson(Utica, N.Y.). As an alternative to shredding, the paper can be reducedin size by cutting to a desired size using a guillotine cutter. Forexample, the guillotine cutter can be used to cut the paper into sheetsthat are, e.g., 10 inches wide by 12 inches long.

In some cases, multiple shredder-shearer trains can be arranged inseries, for example two shredder-shearer trains can be arranged inseries with output from the first shearer fed as input to the secondshredder. In another embodiment, three shredder-shearer trains can bearranged in series with output from the first shearer fed as input tothe second shredder and output from the second shearer fed as input tothe third shredder. Multiple passes through shredder-shearer trains candecrease particle size and increase overall surface area.

In some embodiments, the shearing of fiber source and the passing of theresulting first fibrous material through first screen are performedconcurrently. The shearing and the passing can also be performed in abatch-type process.

For example, a rotary knife cutter can be used to concurrently shear thefiber source and screen the first fibrous material. Referring to FIG. 3,a rotary knife cutter 220 includes a hopper 222 that can be loaded witha shredded fiber source 224 prepared by shredding fiber source. Shreddedfiber source is sheared between stationary blades 230 and rotatingblades 232 to provide a first fibrous material 240. First fibrousmaterial 240 passes through screen 242, and the resulting second fibrousmaterial 244 is captured in bin 250. To aid in the collection of thesecond fibrous material, the bin can have a pressure below nominalatmospheric pressure, e.g., at least 10 percent below nominalatmospheric pressure, e.g., at least 25 percent below nominalatmospheric pressure, at least 50 percent below nominal atmosphericpressure, or at least 75 percent below nominal atmospheric pressure. Insome embodiments, a vacuum source 252 is utilized to maintain the binbelow nominal atmospheric pressure.

Shearing can be advantageous for “opening up” and “stressing” thefibrous materials, making the cellulose of the materials moresusceptible to chain scission and/or reduction of crystallinity. Theopen materials can also be more susceptible to oxidation whenirradiated.

The fiber source can be sheared in a dry state, a hydrated state (e.g.,having up to ten percent by weight absorbed water), or in a wet state,e.g., having between about 10 percent and about 75 percent by weightwater. The fiber source can even be sheared while partially or fullysubmerged under a liquid, such as water, ethanol, isopropanol.

The fiber source can also be sheared in under a gas (such as a stream oratmosphere of gas other than air), e.g., oxygen or nitrogen, or steam.

Other methods of making the fibrous materials include, e.g., stonegrinding, mechanical ripping or tearing, pin grinding or air attritionmilling.

If desired, the fibrous materials can be separated, e.g., continuouslyor in batches, into fractions according to their length, width, density,material type, or some combination of these attributes. For example, forforming composites, it is often desirable to have a relatively narrowdistribution of fiber lengths.

For example, ferrous materials can be separated from any of the fibrousmaterials by passing a fibrous material that includes a ferrous materialpast a magnet, e.g., an electromagnet, and then passing the resultingfibrous material through a series of screens, each screen havingdifferent sized apertures.

The fibrous materials can also be separated, e.g., by using a highvelocity gas, e.g., air. In such an approach, the fibrous materials areseparated by drawing off different fractions, which can be characterizedphotonically, if desired. Such a separation apparatus is discussed inLindsey et al, U.S. Pat. No. 6,883,667.

The fibrous materials can irradiated immediately following theirpreparation, or they can may be dried, e.g., at approximately 105° C.for 4-18 hours, so that the moisture content is, e.g., less than about0.5% before use.

If desired, lignin can be removed from any of the fibrous materials thatinclude lignin. Also, to aid in the breakdown of the materials thatinclude the cellulose, the material can be treated prior to irradiationwith heat, a chemical (e.g., mineral acid, base or a strong oxidizersuch as sodium hypochlorite) and/or an enzyme.

In some embodiments, the average opening size of the first screen isless than 0.79 mm ( 1/32 inch, 0.03125 inch), e.g., less than 0.51 mm (1/50 inch, 0.02000 inch), less than 0.40 mm ( 1/64 inch, 0.015625 inch),less than 0.23 mm (0.009 inch), less than 0.20 mm ( 1/128 inch,0.0078125 inch), less than 0.18 mm (0.007 inch), less than 0.13 mm(0.005 inch), or even less than less than 0.10 mm ( 1/256 inch,0.00390625 inch). The screen is prepared by interweaving monofilamentshaving an appropriate diameter to give the desired opening size. Forexample, the monofilaments can be made of a metal, e.g., stainlesssteel. As the opening sizes get smaller, structural demands on themonofilaments may become greater. For example, for opening sizes lessthan 0.40 mm, it can be advantageous to make the screens frommonofilaments made from a material other than stainless steel, e.g.,titanium, titanium alloys, amorphous metals, nickel, tungsten, rhodium,rhenium, ceramics, or glass. In some embodiments, the screen is madefrom a plate, e.g. a metal plate, having apertures, e.g., cut into theplate using a laser. In some embodiments, the open area of the mesh isless than 52%, e.g., less than 41%, less than 36%, less than 31%, lessthan 30%.

In some embodiments, the second fibrous is sheared and passed throughthe first screen, or a different sized screen. In some embodiments, thesecond fibrous material is passed through a second screen having anaverage opening size equal to or less than that of first screen.

Referring to FIG. 4, a third fibrous material 220 can be prepared fromthe second fibrous material 216 by shearing the second fibrous material216 and passing the resulting material through a second screen 222having an average opening size less than the first screen 214.

Generally, the fibers of the fibrous materials can have a relativelylarge average length-to-diameter ratio (e.g., greater than 20-to-1),even if they have been sheared more than once. In addition, the fibersof the fibrous materials described herein may have a relatively narrowlength and/or length-to-diameter ratio distribution.

As used herein, average fiber widths (i.e., diameters) are thosedetermined optically by randomly selecting approximately 5,000 fibers.Average fiber lengths are corrected length-weighted lengths. BET(Brunauer, Emmet and Teller) surface areas are multi-point surfaceareas, and porosities are those determined by mercury porosimetry.

The average length-to-diameter ratio of the second fibrous material 14can be, e.g. greater than 8/1, e.g., greater than 10/1, greater than15/1, greater than 20/1, greater than 25/1, or greater than 50/1. Anaverage length of the second fibrous material 14 can be, e.g., betweenabout 0.5 mm and 2.5 mm, e.g., between about 0.75 mm and 1.0 mm, and anaverage width (i.e., diameter) of the second fibrous material 14 can be,e.g., between about 5 μm and 50 μm, e.g., between about 10 μm and 30 μm.

In some embodiments, a standard deviation of the length of the secondfibrous material 14 is less than 60 percent of an average length of thesecond fibrous material 14, e.g., less than 50 percent of the averagelength, less than 40 percent of the average length, less than 25 percentof the average length, less than 10 percent of the average length, lessthan 5 percent of the average length, or even less than 1 percent of theaverage length.

In some embodiments, a BET surface area of the second fibrous materialis greater than 0.1 m²/g, e.g., greater than 0.25 m²/g, greater than 0.5m²/g, greater than 1.0 m²/g, greater than 1.5 m²/g, greater than 1.75m²/g, greater than 5.0 m²/g, greater than 10 m²/g, greater than 25 m²/g,greater than 35 m²/g, greater than 50 m²/g, greater than 60 m²/g,greater than 75 m²/g, greater than 100 m²/g, greater than 150 m²/g,greater than 200 m²/g, or even greater than 250 m²/g. A porosity of thesecond fibrous material 14 can be, e.g., greater than 20 percent,greater than 25 percent, greater than 35 percent, greater than 50percent, greater than 60 percent, greater than 70 percent, e.g., greaterthan 80 percent, greater than 85 percent, greater than 90 percent,greater than 92 percent, greater than 94 percent, greater than 95percent, greater than 97.5 percent, greater than 99 percent, or evengreater than 99.5 percent.

In some embodiments, a ratio of the average length-to-diameter ratio ofthe first fibrous material to the average length-to-diameter ratio ofthe second fibrous material is, e.g., less than 1.5, e.g., less than1.4, less than 1.25, less than 1.1, less than 1.075, less than 1.05,less than 1.025, or even substantially equal to 1.

In particular embodiments, the second fibrous material is sheared againand the resulting fibrous material passed through a second screen havingan average opening size less than the first screen to provide a thirdfibrous material. In such instances, a ratio of the averagelength-to-diameter ratio of the second fibrous material to the averagelength-to-diameter ratio of the third fibrous material can be, e.g.,less than 1.5, e.g., less than 1.4, less than 1.25, or even less than1.1.

In some embodiments, the third fibrous material is passed through athird screen to produce a fourth fibrous material. The fourth fibrousmaterial can be, e.g., passed through a fourth screen to produce a fifthmaterial. Similar screening processes can be repeated as many times asdesired to produce the desired fibrous material having the desiredproperties.

Densification

Densified materials can be processed by any of the methods describedherein.

A material, e.g., a fibrous material, having a low bulk density can bedensified to a product having a higher bulk density. For example, amaterial composition having a bulk density of 0.05 g/cm³ can bedensified by sealing the fibrous material in a relatively gasimpermeable structure, e.g., a bag made of polyethylene or a bag made ofalternating layers of polyethylene and a nylon, and then evacuating theentrapped gas, e.g., air, from the structure. After evacuation of theair from the structure, the fibrous material can have, e.g., a bulkdensity of greater than 0.3 g/cm³, e.g., 0.5 g/cm³, 0.6 g/cm³, 0.7 g/cm³or more, e.g., 0.85 g/cm³. After densification, the product canprocessed by any of the methods described herein, e.g., irradiated,e.g., with gamma radiation. This can be advantageous when it isdesirable to transport the material to another location, e.g., a remotemanufacturing plant, where the fibrous material composition can be addedto a solution, e.g., to produce ethanol. After piercing thesubstantially gas impermeable structure, the densified fibrous materialcan revert to nearly its initial bulk density, e.g., greater than 60percent of its initial bulk density, e.g., 70 percent, 80 percent, 85percent or more, e.g., 95 percent of its initial bulk density. To reducestatic electricity in the fibrous material, an anti-static agent can beadded to the material.

In some embodiments, the structure, e.g., bag, is formed of a materialthat dissolves in a liquid, such as water. For example, the structurecan be formed from a polyvinyl alcohol so that it dissolves when incontact with a water-based system. Such embodiments allow densifiedstructures to be added directly to solutions that include amicroorganism, without first releasing the contents of the structure,e.g., by cutting.

Referring to FIG. 5, a biomass material can be combined with any desiredadditives and a binder, and subsequently densified by application ofpressure, e.g., by passing the material through a nip defined betweencounter-rotating pressure rolls or by passing the material through apellet mill. During the application of pressure, heat can optionally beapplied to aid in the densification of the fibrous material. Thedensified material can then be irradiated.

In some embodiments, the material prior to densification has a bulkdensity of less than 0.25 g/cm³, e.g., 0.20 g/cm³, 0.15 g/cm³, 0.10g/cm³, 0.05 g/cm³ or less, e.g., 0.025 g/cm³. Bulk density is determinedusing ASTM D1895B. Briefly, the method involves filling a measuringcylinder of known volume with a sample and obtaining a weight of thesample. The bulk density is calculated by dividing the weight of thesample in grams by the known volume of the cylinder in cubiccentimeters.

The preferred binders include binders that are soluble in water, swollenby water, or that has a glass transition temperature of less 25° C., asdetermined by differential scanning calorimetry. By water-solublebinders, we mean binders having a solubility of at least about 0.05weight percent in water. By water swellable binders, we mean bindersthat increase in volume by more than 0.5 percent upon exposure to water.

In some embodiments, the binders that are soluble or swollen by waterinclude a functional group that is capable of forming a bond, e.g., ahydrogen bond, with the fibers of the fibrous material, e.g., cellulosicfibrous material. For example, the functional group can be a carboxylicacid group, a carboxylate group, a carbonyl group, e.g., of an aldehydeor a ketone, a sulfonic acid group, a sulfonate group, a phosphoric acidgroup, a phosphate group, an amide group, an amine group, a hydroxylgroup, e.g., of an alcohol, and combinations of these groups, e.g., acarboxylic acid group and a hydroxyl group. Specific monomeric examplesinclude glycerin, glyoxal, ascorbic acid, urea, glycine,pentaerythritol, a monosaccharide or a disaccharide, citric acid, andtartaric acid. Suitable saccharides include glucose, sucrose, lactose,ribose, fructose, mannose, arabinose and erythrose. Polymeric examplesinclude polyglycols, polyethylene oxide, polycarboxylic acids,polyamides, polyamines and polysulfonic acids polysulfonates. Specificpolymeric examples include polypropylene glycol (PPG), polyethyleneglycol (PEG), polyethylene oxide, e.g., POLYOX®, copolymers of ethyleneoxide and propylene oxide, polyacrylic acid (PAA), polyacrylamide,polypeptides, polyethylenimine, polyvinylpyridine,poly(sodium-4-styrenesulfonate) andpoly(2-acrylamido-methyl-1-propanesulfonic acid).

In some embodiments, the binder includes a polymer that has a glasstransition temperature less 25° C. Examples of such polymers includethermoplastic elastomers (TPEs). Examples of TPEs include polyetherblock amides, such as those available under the tradename PEBAX®,polyester elastomers, such as those available under the tradenameHYTREL®, and styrenic block copolymers, such as those available underthe tradename KRATON®. Other suitable polymers having a glass transitiontemperature less 25° C. include ethylene vinyl acetate copolymer (EVA),polyolefins, e.g., polyethylene, polypropylene, ethylene-propylenecopolymers, and copolymers of ethylene and alpha olefins, e.g.,1-octene, such as those available under the tradename ENGAGE®. In someembodiments, e.g., when the material is a fiberized polycoated paper,the material is densified without the addition of a separate low glasstransition temperature polymer.

In a particular embodiment, the binder is a lignin, e.g., a natural orsynthetically modified lignin.

A suitable amount of binder added to the material, calculated on a dryweight basis, is, e.g., from about 0.01 percent to about 50 percent,e.g., 0.03 percent, 0.05 percent, 0.1 percent, 0.25 percent, 0.5percent, 1.0 percent, 5 percent, 10 percent or more, e.g., 25 percent,based on a total weight of the densified material. The binder can beadded to the material as a neat, pure liquid, as a liquid having thebinder dissolved therein, as a dry powder of the binder, or as pelletsof the binder.

The densified fibrous material can be made in a pellet mill. Referringto FIG. 6, a pellet mill 300 has a hopper 301 for holding undensifiedmaterial 310 that includes a carbohydrate-containing materials, such ascellulose. The hopper communicates with an auger 312 that is driven byvariable speed motor 314 so that undensified material can be transportedto a conditioner 320 that stirs the undensified material with paddles322 that are rotated by conditioner motor 330. Other ingredients, e.g.,any of the additives and/or fillers described herein, can be added atinlet 332. If desired, heat may be added while the fibrous material isin conditioner. After conditioned, the material passes from theconditioner through a dump chute 340, and to another auger 342. The dumpchute, as controlled by actuator 344, allows for unobstructed passage ofthe material from conditioner to auger. Auger is rotated by motor 346,and controls the feeding of the fibrous material into die and rollerassembly 350. Specifically, the material is introduced into a hollow,cylindrical die 352, which rotates about a horizontal axis and which hasradially extending die holes 250. Die 352 is rotated about the axis bymotor 360, which includes a horsepower gauge, indicating total powerconsumed by the motor. Densified material 370, e.g., in the form ofpellets, drops from chute 372 and are captured and processed, such as byirradiation.

The material, after densification, can be conveniently in the form ofpellets or chips having a variety of shapes. The pellets can then beirradiated. In some embodiments, the pellets or chips are cylindrical inshape, e.g., having a maximum transverse dimension of, e.g., 1 mm ormore, e.g., 2 mm, 3 mm, 5 mm, 8 mm, 10 mm, 15 mm or more, e.g., 25 mm.Another convenient shape for making composites includes pellets or chipsthat are plate-like in form, e.g., having a thickness of 1 mm or more,e.g., 2 mm, 3 mm, 5 mm, 8 mm, 10 mm or more, e.g., 25 mm; a width of,e.g., 5 mm or more, e.g., 10 mm, 15 mm, 25 mm, 30 mm or more, e.g., 50mm; and a length of 5 mm or more, e.g., 10 mm, 15 mm, 25 mm, 30 mm ormore, e.g., 50 mm.

Referring now FIG. 7A-7D, pellets can be made so that they have a hollowinside. As shown, the hollow can be generally in-line with the center ofthe pellet (FIG. 7B), or out of line with the center of the pellet (FIG.7C). Making the pellet hollow inside can increase the rate ofdissolution in a liquid after irradiation.

Referring now to FIG. 7D, the pellet can have, e.g., a transverse shapethat is multi-lobal, e.g., tri-lobal as shown, or tetra-lobal,penta-lobal, hexa-lobal or deca-lobal. Making the pellets in suchtransverse shapes can also increase the rate of dissolution in asolution after irradiation.

In one example, fibrous material is sprayed with water or a dilute stocksolution of POLYOX™ WSR N10 (polyethylene oxide) prepared in water. Thewetted fibrous material is processed through a pellet mill operating atroom temperature, increasing the bulk density of the fibrous material bymore than an order of magnitude.

Pretreatment

Physically prepared feedstock can be pretreated for use in primaryproduction processes by, for example, reducing the average molecularweight and crystallinity of the feedstock and/or increasing the surfacearea and/or porosity of the feedstock. In some embodiments, thecellulosic and/or lignocellulosic material includes a first cellulosehaving a first number average molecular weight and the resultingcarbohydrate includes a second cellulose having a second number averagemolecular weight lower than the first number average molecular weight.For example, the second number average molecular weight is lower thanthe first number average molecular weight by more than about twenty-fivepercent, e.g., 2×, 3×, 5×, 7×, 10×, 25×, even 100× reduction.

In some embodiments, the first cellulose has a first crystallinity andthe second cellulose has a second crystallinity lower than the firstcrystallinity, such as lower than about two, three, five, ten, fifteenor twenty-five percent lower.

In some embodiments, the first cellulose has a first level of oxidationand the second cellulose has a second level of oxidation higher than thefirst level of oxidation, such as two, three, four, five, ten or eventwenty-five percent higher.

Pretreatment processes can include one or more of irradiation,sonication, oxidation, pyrolysis, and steam explosion. The variouspretreatment systems and methods can be used in combinations of two,three, or even four of these technologies.

Pretreatment Combinations

In some embodiments, biomass can be processed by applying two, three,four or more of any of the processes described herein, such as two ormore of radiation, sonication, oxidation, pyrolysis, and steam explosioneither with or without prior, intermediate, or subsequent feedstockpreparation as described herein. The processes can be applied in anyorder (or concurrently) to the biomass, e.g., a cellulosic and/orlignocellulosic material. For example, a carbohydrate can be prepared byapplying radiation, sonication, oxidation, pyrolysis, and, optionally,steam explosion to a cellulosic and/or lignocellulosic material (in anyorder or concurrently). The provided carbohydrate-containing materialcan then be converted by one or more microorganisms, such as bacteria,yeast, or mixtures of yeast and bacteria, to a number of desirableproducts, as described herein. Multiple processes can provide materialsthat can be more readily utilized by a variety of microorganisms becauseof their lower molecular weight, lower crystallinity, and/or enhancedsolubility. Multiple processes can provide synergies and can reduceoverall energy input required in comparison to any single process.

For example, in some embodiments, feedstocks are provided that include acarbohydrate that is produced by a process that includes irradiating andsonicating, irradiating and oxidizing, irradiating and pyrolyzing, orirradiating and steam-exploding (in either order or concurrently) acellulosic and/or a lignocellulosic material. The provided feedstock canthen be contacted with a microorganism having the ability to convert atleast a portion, e.g., at least about 1 percent by weight, of thefeedstock to the product, such as the combustible fuel.

Pretreatment Conditions

In some embodiments, the process does not include hydrolyzing thecellulosic and/or lignocellulosic material, such as with an acid or abase, e.g., a mineral acid, such as hydrochloric or sulfuric acid.

If desired, some or none of the feedstock can include a hydrolyzedmaterial. For example, in some embodiments, at least about seventypercent by weight of the feedstock is an unhydrolyzed material, e.g., atleast at 95 percent by weight of the feedstock is an unhydrolyzedmaterial. In some embodiments, substantially all of the feedstock is anunhydrolyzed material.

Any feedstock or any reactor or fermentor charged with a feedstock caninclude a buffer, such as sodium bicarbonate, ammonium chloride or Tris;an electrolyte, such as potassium chloride, sodium chloride, or calciumchloride; a growth factor, such as biotin and/or a base pair such asuracil or an equivalent thereof; a surfactant, such as Tween® orpolyethylene glycol; a mineral, such as such as calcium, chromium,copper, iodine, iron, selenium, or zinc; or a chelating agent, such asethylene diamine, ethylene diamine tetraacetic acid (EDTA) (or its saltform, e.g., sodium or potassium EDTA), or dimercaprol.

When radiation is utilized, it can be applied to any sample that is dryor wet, or even dispersed in a liquid, such as water. For example,irradiation can be performed on cellulosic and/or lignocellulosicmaterial in which less than about 25 percent by weight of the cellulosicand/or lignocellulosic material has surfaces wetted with a liquid, suchas water. In some embodiments, irradiating is performed on cellulosicand/or lignocellulosic material in which substantially none of thecellulosic and/or lignocellulosic material is wetted with a liquid, suchas water.

In some embodiments, any processing described herein occurs after thecellulosic and/or lignocellulosic material remains dry as acquired orhas been dried, e.g., using heat and/or reduced pressure. For example,in some embodiments, the cellulosic and/or lignocellulosic material hasless than about five percent by weight retained water, measured at 25°C. and at fifty percent relative humidity.

If desired, a swelling agent, as defined herein, can be utilized in anyprocess described herein. In some embodiments, when a cellulosic and/orlignocellulosic material is processed using radiation, less than about25 percent by weight of the cellulosic and/or lignocellulosic materialis in a swollen state, the swollen state being characterized as having avolume of more than about 2.5 percent higher than an unswollen state,e.g., more than 5.0, 7.5, 10, or 15 percent higher than the unswollenstate. In some embodiments, when radiation is utilized on a cellulosicand/or lignocellulosic material, substantially none of the cellulosicand/or lignocellulosic material is in a swollen state.

In specific embodiments when radiation is utilized, the cellulosicand/or lignocellulosic material includes a swelling agent, and swollencellulosic and/or lignocellulosic receives a dose of less than about 10Mrad.

When radiation is utilized in any process, it can be applied while thecellulosic and/or lignocellulosic is exposed to air, oxygen-enrichedair, or even oxygen itself, or blanketed by an inert gas such asnitrogen, argon, or helium. When maximum oxidation is desired, anoxidizing environment is utilized, such as air or oxygen.

When radiation is utilized, it may be applied to biomass, such ascellulosic and/or lignocellulosic material, under a pressure of greaterthan about 2.5 atmospheres, such as greater than 5, 10, 15, 20, or evengreater than about 50 atmospheres.

In specific embodiments, the process includes irradiating and sonicatingand irradiating precedes sonicating. In other specific embodiments,sonication precedes irradiating, or irradiating and sonicating occurconcurrently.

In some embodiments, the process includes irradiating and sonicating (ineither order or concurrently) and further includes oxidizing, pyrolyzingor steam exploding.

When the process includes radiation, the irradiating can be performedutilizing an ionizing radiation, such as gamma rays, x-rays, energeticultraviolet radiation, such as ultraviolet C radiation having awavelength of from about 100 nm to about 280 nm, a beam of particles,such as a beam of electrons, slow neutrons or alpha particles. In someembodiments, irradiating includes two or more radiation sources, such asgamma rays and a beam of electrons, which can be applied in either orderor concurrently.

In specific embodiments, sonicating can performed at a frequency ofbetween about 15 khz and about 25 khz, such as between about 18 khz and22 khz utilizing a 1 KW or larger horn, e.g., a 2, 3, 4, 5, or even a 10KW horn.

Any processing technique described herein can be used at pressure aboveor below normal, earth-bound atmospheric pressure. For example, anyprocess that utilizes radiation, sonication, oxidation, pyrolysis, steamexplosion, or combinations of any of these processes to providematerials that include a carbohydrate can be performed under highpressure, which, can increase reaction rates. For example, any processor combination of processes can be performed at a pressure greater thanabout greater than 25 MPa, e.g., greater than 50 MPa, 75 MPa, 100 MPa,150 MPa, 200 MPa, 250 MPa, 350 MPa, 500 MPa, 750 MPa, 1,000 MPa, orgreater than 1,500 MPa.

In one example of the use of radiation with oxidation as a pretreatment,half-gallon juice cartons made of un-printed polycoated white Kraftboard having a bulk density of 20 lb/ft³ are used as a feedstock.Cartons are folded flat and then fed into a sequence of threeshredder-shearer trains arranged in series with output from the firstshearer fed as input to the second shredder, and output from the secondshearer fed as input to the third shredder. The resulting fibrousmaterial is sprayed with water and processed through a pellet milloperating at room temperature, producing densified pellets that areplaced in a glass ampoule which is sealed under an atmosphere of air.The pellets in the ampoule are irradiated with gamma radiation for about3 hours at a dose rate of about 1 Mrad per hour to provide an irradiatedmaterial in which the cellulose has a lower molecular weight than thefibrous Kraft starting material.

Radiation Treatment

One or more irradiation processing sequences can be used to process rawfeedstock from a wide variety of different sources to extract usefulsubstances from the feedstock, and to provide partially degraded organicmaterial which functions as input to further processing steps and/orsequences. Irradiation can reduce the molecular weight and/orcrystallinity of feedstock. In some embodiments, energy deposited in amaterial that releases an electron from its atomic orbital is used toirradiate the materials. The radiation may be provided by 1) heavycharged particles, such as alpha particles, 2) electrons, produced, forexample, in beta decay or electron beam accelerators, or 3)electromagnetic radiation, for example, gamma rays, x rays, orultraviolet rays. In one approach, radiation produced by radioactivesubstances can be used to irradiate the feedstock. In another approach,electromagnetic radiation (e.g., produced using electron beam emitters)can be used to irradiate the feedstock. The doses applied depend on thedesired effect and the particular feedstock. For example, high doses ofradiation can break chemical bonds within feedstock components and lowdoses of radiation can increase chemical bonding (e.g., cross-linking)within feedstock components.

Referring to FIG. 8, in one method, a first material 2 that is orincludes cellulose having a first number average molecular weight(^(T)M_(N1)) is irradiated, e.g., by treatment with ionizing radiation(e.g., in the form of gamma radiation, X-ray radiation, 100 nm to 280 nmultraviolet (UV) light, a beam of electrons or other charged particles)to provide a second material 3 that includes cellulose having a secondnumber average molecular weight (^(T)M_(N2)) lower than the first numberaverage molecular weight. The second material (or the first and secondmaterial) can be combined with a microorganism (e.g., a bacterium or ayeast) that can utilize the second and/or first material to produce afuel 5 that is or includes hydrogen, an alcohol (e.g., ethanol orbutanol, such as n-, sec-or t-butanol), an organic acid, a hydrocarbonor mixtures of any of these.

Since the second material 3 has cellulose having a reduced molecularweight relative to the first material, and in some instances, a reducedcrystallinity as well, the second material is generally moredispersible, swellable and/or soluble in a solution containing amicroorganism. These properties make the second material 3 moresusceptible to chemical, enzymatic and/or biological attack relative tothe first material 2, which can greatly improve the production rateand/or production level of a desired product, e.g., ethanol. Radiationcan also sterilize the materials.

In some embodiments, the second number average molecular weight (M_(N2))is lower than the first number average molecular weight (^(T)M_(N1)) bymore than about 10 percent, e.g., 15, 20, 25, 30, 35, 40, 50 percent, 60percent, or even more than about 75 percent.

In some instances, the second material has cellulose that has ascrystallinity (^(T)C₂) that is lower than the crystallinity (^(T)C₁) ofthe cellulose of the first material. For example, (^(T)C₂) can be lowerthan (^(T)C₁) by more than about 10 percent, e.g., 15, 20, 25, 30, 35,40, or even more than about 50 percent.

In some embodiments, the starting crystallinity index (prior toirradiation) is from about 40 to about 87.5 percent, e.g., from about 50to about 75 percent or from about 60 to about 70 percent, and thecrystallinity index after irradiation is from about 10 to about 50percent, e.g., from about 15 to about 45 percent or from about 20 toabout 40 percent. However, in some embodiments, e.g., after extensiveirradiation, it is possible to have a crystallinity index of lower than5 percent. In some embodiments, the material after irradiation issubstantially amorphous.

In some embodiments, the starting number average molecular weight (priorto irradiation) is from about 200,000 to about 3,200,000, e.g., fromabout 250,000 to about 1,000,000 or from about 250,000 to about 700,000,and the number average molecular weight after irradiation is from about50,000 to about 200,000, e.g., from about 60,000 to about 150,000 orfrom about 70,000 to about 125,000. However, in some embodiments, e.g.,after extensive irradiation, it is possible to have a number averagemolecular weight of less than about 10,000 or even less than about5,000.

In some embodiments, the second material can have a level of oxidation(^(T)O₂) that is higher than the level of oxidation (^(T)O₁) of thefirst material. A higher level of oxidation of the material can aid inits dispersability, swellability and/or solubility, further enhancingthe materials susceptibility to chemical, enzymatic or biologicalattack. In some embodiments, to increase the level of the oxidation ofthe second material relative to the first material, the irradiation isperformed under an oxidizing environment, e.g., under a blanket of airor oxygen, producing a second material that is more oxidized than thefirst material. For example, the second material can have more hydroxylgroups, aldehyde groups, ketone groups, ester groups or carboxylic acidgroups, which can increase its hydrophilicity.

Ionizing Radiation

Each form of radiation ionizes the biomass via particular interactions,as determined by the energy of the radiation. Heavy charged particlesprimarily ionize matter via Coulomb scattering; furthermore, theseinteractions produce energetic electrons that may further ionize matter.Alpha particles are identical to the nucleus of a helium atom and areproduced by the alpha decay of various radioactive nuclei, such asisotopes of bismuth, polonium, astatine, radon, francium, radium,several actinides, such as actinium, thorium, uranium, neptunium,curium, californium, americium, and plutonium.

Electrons interact via Coulomb scattering and bremsstrahlung radiationproduced by changes in the velocity of electrons. Electrons may beproduced by radioactive nuclei that undergo beta decay, such as isotopesof iodine, cesium, technetium, and iridium. Alternatively, an electrongun can be used as an electron source via thermionic emission.

Electromagnetic radiation interacts via three processes: photoelectricabsorption, Compton scattering, and pair production. The dominatinginteraction is determined by the energy of the incident radiation andthe atomic number of the material. The summation of interactionscontributing to the absorbed radiation in cellulosic material can beexpressed by the mass absorption coefficient.

Electromagnetic radiation is subclassified as gamma rays, x rays,ultraviolet rays, infrared rays, microwaves, or radiowaves, depending onits wavelength.

For example, gamma radiation can be employed to irradiate the materials.Referring to FIGS. 9 and 10 (an enlarged view of region R), a gammairradiator 10 includes gamma radiation sources 408, e.g., ⁶⁰Co pellets,a working table 14 for holding the materials to be irradiated andstorage 16, e.g., made of a plurality iron plates, all of which arehoused in a concrete containment chamber 20 that includes a mazeentranceway 22 beyond a lead-lined door 26. Storage 16 includes aplurality of channels 30, e.g., sixteen or more channels, allowing thegamma radiation sources to pass through storage on their way proximatethe working table.

In operation, the sample to be irradiated is placed on a working table.The irradiator is configured to deliver the desired dose rate andmonitoring equipment is connected to an experimental block 31. Theoperator then leaves the containment chamber, passing through the mazeentranceway and through the lead-lined door. The operator mans a controlpanel 32, instructing a computer 33 to lift the radiation sources 12into working position using cylinder 36 attached to a hydraulic pump 40.

Gamma radiation has the advantage of a significant penetration depthinto a variety of material in the sample. Sources of gamma rays includeradioactive nuclei, such as isotopes of cobalt, calcium, technicium,chromium, gallium, indium, iodine, iron, krypton, samarium, selenium,sodium, thalium, and xenon.

Sources of x rays include electron beam collision with metal targets,such as tungsten or molybdenum or alloys, or compact light sources, suchas those produced commercially by Lyncean.

Sources for ultraviolet radiation include deuterium or cadmium lamps.

Sources for infrared radiation include sapphire, zinc, or selenidewindow ceramic lamps.

Sources for microwaves include klystrons, Slevin type RF sources, oratom beam sources that employ hydrogen, oxygen, or nitrogen gases.

Electron Beam

In some embodiments, a beam of electrons is used as the radiationsource. A beam of electrons has the advantages of high dose rates (e.g.,1, 5, or even 10 Mrad per second), high throughput, less containment,and less confinement equipment. Electrons can also be more efficient atcausing chain scission. In addition, electrons having energies of 4-10MeV can have a penetration depth of 5 to 30 mm or more, such as 40 mm.

Electron beams can be generated, e.g., by electrostatic generators,cascade generators, transformer generators, low energy accelerators witha scanning system, low energy accelerators with a linear cathode, linearaccelerators, and pulsed accelerators. Electrons as an ionizingradiation source can be useful, e.g., for relatively thin piles ofmaterials, e.g., less than 0.5 inch, e.g., less than 0.4 inch, 0.3 inch,0.2 inch, or less than 0.1 inch. In some embodiments, the energy of eachelectron of the electron beam is from about 0.3 MeV to about 2.0 MeV(million electron volts), e.g., from about 0.5 MeV to about 1.5 MeV, orfrom about 0.7 MeV to about 1.25 MeV.

FIG. 11 shows a process flow diagram 3000 that includes various steps inan electron beam irradiation feedstock pretreatment sequence. In firststep 3010, a supply of dry feedstock is received from a feed source. Asdiscussed above, the dry feedstock from the feed source may bepre-processed prior to delivery to the electron beam irradiationdevices. For example, if the feedstock is derived from plant sources,certain portions of the plant material may be removed prior tocollection of the plant material and/or before the plant material isdelivered by the feedstock transport device. Alternatively, or inaddition, as expressed in optional step 3020, the biomass feedstock canbe subjected to mechanical processing (e.g., to reduce the averagelength of fibers in the feedstock) prior to delivery to the electronbeam irradiation devices.

In step 3030, the dry feedstock is transferred to a feedstock transportdevice (e.g., a conveyor belt) and is distributed over thecross-sectional width of the feedstock transport device approximatelyuniformly by volume. This can be accomplished, for example, manually orby inducing a localized vibration motion at some point in the feedstocktransport device prior to the electron beam irradiation processing.

In some embodiments, a mixing system introduces a chemical agent 3045into the feedstock in an optional process 3040 that produces a slurry.Combining water with the processed feedstock in mixing step 3040 createsan aqueous feedstock slurry that may be transported through, forexample, piping rather than using, for example, a conveyor belt.

The next step 3050 is a loop that encompasses exposing the feedstock (indry or slurry form) to electron beam radiation via one or more (say, N)electron beam irradiation devices. The feedstock slurry is moved througheach of the N “showers” of electron beams at step 3052. The movement mayeither be at a continuous speed through and between the showers, orthere may be a pause through each shower, followed by a sudden movementto the next shower. A small slice of the feedstock slurry is exposed toeach shower for some predetermined exposure time at step 3053.

Electron beam irradiation devices may be procured commercially from IonBeam Applications, Louvain-la-Neuve, Belgium or the Titan Corporation,San Diego, Calif. Typical electron energies can be 1 MeV, 2 MeV, 4.5MeV, 7.5 MeV, or 10 MeV. Typical electron beam irradiation device powercan be 1 kW, 5 kW, 10 kW, 20 kW, 50 kW, 100 kW, 250 kW, or 500 kW.Effectiveness of depolymerization of the feedstock slurry depends on theelectron energy used and the dose applied, while exposure time dependson the power and dose. Typical doses may take values of 1 kGy, 5 kGy, 10kGy, 20 kGy, 50 kGy, 100 kGy, or 200 kGy.

Tradeoffs in considering electron beam irradiation device powerspecifications include cost to operate, capital costs, depreciation, anddevice footprint. Tradeoffs in considering exposure dose levels ofelectron beam irradiation would be energy costs and environment, safety,and health (ESH) concerns. Tradeoffs in considering electron energiesinclude energy costs; here, a lower electron energy may be advantageousin encouraging depolymerization of certain feedstock slurry (see, forexample, Bouchard, et al, Cellulose (2006) 13: 601-610).

It may be advantageous to provide a double-pass of electron beamirradiation in order to provide a more effective depolymerizationprocess. For example, the feedstock transport device could direct thefeedstock (in dry or slurry form) underneath and in a reverse directionto its initial transport direction. Double-pass systems can allowthicker feedstock slurries to be processed and can provide a moreuniform depolymerization through the thickness of the feedstock slurry.

The electron beam irradiation device can produce either a fixed beam ora scanning beam. A scanning beam may be advantageous with large scansweep length and high scan speeds, as this would effectively replace alarge, fixed beam width. Further, available sweep widths of 0.5 m, 1 m,2 m or more are available.

Once a portion of feedstock slurry has been transported through the Nelectron beam irradiation devices, it may be necessary in someembodiments, as in step 3060, to mechanically separate the liquid andsolid components of the feedstock slurry. In these embodiments, a liquidportion of the feedstock slurry is filtered for residual solid particlesand recycled back to the slurry preparation step 3040. A solid portionof the feedstock slurry is then advanced on to the next processing step3070 via the feedstock transport device. In other embodiments, thefeedstock is maintained in slurry form for further processing.

Electromagnetic Radiation

In embodiments in which the irradiating is performed withelectromagnetic radiation, the electromagnetic radiation can have, e.g.,energy per photon (in electron volts) of greater than 10² eV, e.g.,greater than 10³, 10⁴, 10⁵, 10⁶, or even greater than 10⁷ eV. In someembodiments, the electromagnetic radiation has energy per photon ofbetween 10⁴ and 10⁷, e.g., between 10⁵ and 10⁶ eV. The electromagneticradiation can have a frequency of, e.g., greater than 10¹⁶ Hz, greaterthan 10¹⁷ Hz, 10¹⁸, 10¹⁹, 10²⁰, or even greater than 10²¹ Hz. In someembodiments, the electromagnetic radiation has a frequency of between10¹⁸ and 10²² Hz, e.g., between 10¹⁹ to 10²¹ Hz.

Doses

In some embodiments, the irradiating (with any radiation source or acombination of sources) is performed until the material receives a doseof at least 0.25 Mrad, e.g., at least 1.0 Mrad, at least 2.5 Mrad, atleast 5.0 Mrad, or at least 10.0 Mrad. In some embodiments, theirradiating is performed until the material receives a dose of between1.0 Mrad and 6.0 Mrad, e.g., between 1.5 Mrad and 4.0 Mrad.

In some embodiments, the irradiating is performed at a dose rate ofbetween 5.0 and 1500.0 kilorads/hour, e.g., between 10.0 and 750.0kilorads/hour or between 50.0 and 350.0 kilorads/hours.

In some embodiments, two or more radiation sources are used, such as twoor more ionizing radiations. For example, samples can be treated, in anyorder, with a beam of electrons, followed by gamma radiation and UVlight having wavelengths from about 100 nm to about 280 nm. In someembodiments, samples are treated with three ionizing radiation sources,such as a beam of electrons, gamma radiation, and energetic UV light.

In some embodiments, relatively low doses of radiation can crosslink,graft, or otherwise increase the molecular weight of acarbohydrate-containing material, such as a cellulosic orlignocellulosic material (e.g., cellulose). Such a material havingincreased molecular weight can be useful, e.g., in making a composite,e.g., having improved mechanical properties, such as abrasionresistance, compression strength, fracture resistance, impact strength,bending strength, tensile modulus, flexural modulus and elongation atbreak. Such a material having increased molecular weight can be usefulin making a composition.

For example, a fibrous material that includes a first cellulosic and/orlignocellulosic material having a first molecular weight can beirradiated in such a manner as to provide a second cellulosic and/orlignocellulosic material having a second molecular weight higher thanthe first molecular weight. For example, if gamma radiation is utilizedas the radiation source, a dose of from about 1 Mrad to about 10 Mrad,e.g., from about 1.5 Mrad to about 7.5 Mrad or from about 2.0 Mrad toabout 5.0 Mrad, can be applied. After the low dose of radiation, thesecond cellulosic and/or lignocellulosic material can be combined with aresin and formed into a composite, e.g., by compression molding,injection molding or extrusion. Forming composites is described in WO2006/102543, and in U.S. Provisional Patent Application Ser. Nos.60/664,832, filed on Mar. 24, 2005, 60/688,002, filed on Jun. 7, 2005,60/711,057, filed on Aug. 24, 2005, 60/715,822, filed on Sep. 9, 2005,60/725,674, filed on Oct. 12, 2005, 60/726,102, filed on Oct. 12, 2005,and 60/750,205, filed on Dec. 13, 2005.

Alternatively, a fibrous material that includes a first cellulosicand/or lignocellulosic material having a first molecular weight can becombined with a resin to provide a composite, and then the composite canbe irradiated with a relatively low dose of radiation so as to provide asecond cellulosic and/or lignocellulosic material having a secondmolecular weight higher than the first molecular weight. For example, ifgamma radiation is utilized as the radiation source, a dose of fromabout 1 Mrad to about 10 Mrad can be applied. Using this approachincreases the molecular weight of the material while it is with a resinmatrix. In some embodiments, the resin is a cross-linkable resin and assuch it crosslinks as the carbohydrate-containing material increases inmolecular weight, which can provide a synergistic effect to providemaximum mechanical properties to the composite. For example, suchcomposites can have excellent low temperature performance, e.g., havinga reduced tendency to break and/or crack at low temperatures, e.g.,temperatures below 0° C., e.g., below −10° C., −20° C., −40° C., −50°C., −60° C. or even below −100° C., and/or excellent performance at hightemperatures, e.g., capable of maintaining their advantageous mechanicalproperties at relatively high temperature, e.g., at temperatures above100° C., e.g., above 125° C., 150° C., 200° C., 250° C., 300° C., 400°C., or even above 500° C. In addition, such composites can haveexcellent chemical resistance, e.g., resistance to swelling in asolvent, e.g., a hydrocarbon solvent, resistance to chemical attack,e.g., by strong acids, strong bases, strong oxidants (e.g., chlorine orbleach) or reducing agents (e.g., active metals such as sodium andpotassium).

Alternatively, in another example, a fibrous material that includes acellulosic and/or lignocellulosic material is irradiated and,optionally, treated with acoustic energy, e.g., ultrasound.

In one example of the use of radiation as a pretreatment, half-gallonjuice cartons made of un-printed polycoated white Kraft board having abulk density of 20 lb/ft³ are used as a feedstock. Cartons are foldedflat and then fed into a sequence of three shredder-shearer trainsarranged in series with output from the first shearer fed as input tothe second shredder, and output from the second shearer fed as input tothe third shredder. The fibrous material produced by the can be sprayedwith water and processed through a pellet mill operating at roomtemperature. The densified pellets can be placed in a glass ampoulewhich is evacuated under high vacuum and then back-filled with argongas. The ampoule is sealed under argon. The pellets in the ampoule areirradiated with gamma radiation for about 3 hours at a dose rate ofabout 1 Mrad per hour to provide an irradiated material in which thecellulose has a lower molecular weight than the starting material.

Sonication

One or more sonication processing sequences can be used to process rawfeedstock from a wide variety of different sources to extract usefulsubstances from the feedstock, and to provide partially degraded organicmaterial which functions as input to further processing steps and/orsequences. Sonication can reduce the molecular weight and/orcrystallinity of feedstock.

Referring again to FIG. 8, in one method, a first material 2 thatincludes cellulose having a first number average molecular weight(^(T)M_(N1)) is dispersed in a medium, such as water, and sonicatedand/or otherwise cavitated, to provide a second material 3 that includescellulose having a second number average molecular weight (^(T)M_(N2))lower than the first number average molecular weight. The secondmaterial (or the first and second material in certain embodiments) canbe combined with a microorganism (e.g., a bacterium or a yeast) that canutilize the second and/or first material to produce a fuel 5 that is orincludes hydrogen, an alcohol, an organic acid, a hydrocarbon ormixtures of any of these.

Since the second material has cellulose having a reduced molecularweight relative to the first material, and in some instances, a reducedcrystallinity as well, the second material is generally moredispersible, swellable, and/or soluble in a solution containing themicroorganism, e.g., at a concentration of greater than 10⁶microorganisms/mL. These properties make the second material 3 moresusceptible to chemical, enzymatic, and/or microbial attack relative tothe first material 2, which can greatly improve the production rateand/or production level of a desired product, e.g., ethanol. Sonicationcan also sterilize the materials, but should not be used while themicroorganisms are supposed to be alive.

In some embodiments, the second number average molecular weight(^(T)M_(N2)) is lower than the first number average molecular weight(^(T)M_(N2)) by more than about 10 percent, e.g., 15, 20, 25, 30, 35,40, 50 percent, 60 percent, or even more than about 75 percent.

In some instances, the second material has cellulose that has ascrystallinity (^(T)C₂) that is lower than the crystallinity (^(T)C₁) ofthe cellulose of the first material. For example, (^(T)C₂) can be lowerthan (^(T)C₁) by more than about 10 percent, e.g., 15, 20, 25, 30, 35,40, or even more than about 50 percent.

In some embodiments, the starting crystallinity index (prior tosonication) is from about 40 to about 87.5 percent, e.g., from about 50to about 75 percent or from about 60 to about 70 percent, and thecrystallinity index after sonication is from about 10 to about 50percent, e.g., from about 15 to about 45 percent or from about 20 toabout 40 percent. However, in certain embodiments, e.g., after extensivesonication, it is possible to have a crystallinity index of lower than 5percent. In some embodiments, the material after sonication issubstantially amorphous.

In some embodiments, the starting number average molecular weight (priorto sonication) is from about 200,000 to about 3,200,000, e.g., fromabout 250,000 to about 1,000,000 or from about 250,000 to about 700,000,and the number average molecular weight after sonication is from about50,000 to about 200,000, e.g., from about 60,000 to about 150,000 orfrom about 70,000 to about 125,000. However, in some embodiments, e.g.,after extensive sonication, it is possible to have a number averagemolecular weight of less than about 10,000 or even less than about5,000.

In some embodiments, the second material can have a level of oxidation(^(T)O₂) that is higher than the level of oxidation (^(T)O₁) of thefirst material. A higher level of oxidation of the material can aid inits dispersability, swellability and/or solubility, further enhancingthe materials susceptibility to chemical, enzymatic or microbial attack.In some embodiments, to increase the level of the oxidation of thesecond material relative to the first material, the sonication isperformed in an oxidizing medium, producing a second material that ismore oxidized than the first material. For example, the second materialcan have more hydroxyl groups, aldehyde groups, ketone groups, estergroups or carboxylic acid groups, which can increase its hydrophilicity.

In some embodiments, the sonication medium is an aqueous medium. Ifdesired, the medium can include an oxidant, such as a peroxide (e.g.,hydrogen peroxide), a dispersing agent and/or a buffer. Examples ofdispersing agents include ionic dispersing agents, e.g., sodium laurylsulfate, and non-ionic dispersing agents, e.g., poly(ethylene glycol).

In other embodiments, the sonication medium is non-aqueous. For example,the sonication can be performed in a hydrocarbon, e.g., toluene orheptane, an ether, e.g., diethyl ether or tetrahydrofuran, or even in aliquefied gas such as argon, xenon, or nitrogen.

Without wishing to be bound by any particular theory, it is believedthat sonication breaks bonds in the cellulose by creating bubbles in themedium containing the cellulose, which grow and then violently collapse.During the collapse of the bubble, which can take place in less than ananosecond, the implosive force raises the local temperature within thebubble to about 5100 K (even higher in some instance; see, e.g., Suslicket al., Nature 434, 52-55) and generates pressures of from a few hundredatmospheres to over 1000 atmospheres or more. It is these hightemperatures and pressures that break the bonds. In addition, withoutwishing to be bound by any particular theory, it is believed thatreduced crystallinity arises, at least in part, from the extremely highcooling rates during collapse of the bubbles, which can be greater thanabout 10¹¹ K/second. The high cooling rates generally do not allow thecellulose to organize and crystallize, resulting in materials that havereduced crystallinity. Ultrasonic systems and sonochemistry arediscussed in, e.g., Olli et al., U.S. Pat. No. 5,766,764; Roberts, U.S.Pat. No. 5,828,156; Mason, Chemistry with Ultrasound, Elsevier, Oxford,(1990); Suslick (editor), Ultrasound: its Chemical, Physical andBiological Effects, VCH, Weinheim, (1988); Price, “Current Trends inSonochemistry” Royal Society of Chemistry, Cambridge, (1992); Suslick etal., Ann. Rev. Mater. Sci. 29, 295, (1999); Suslick et al., Nature 353,414 (1991); Hiller et al., Phys. Rev. Lett. 69, 1182 (1992); Barber etal., Nature, 352, 414 (1991); Suslick et al., J. Am. Chem. Soc., 108,5641 (1986); Tang et al., Chem. Comm., 2119 (2000); Wang et al.,Advanced Mater., 12, 1137 (2000); Landau et al., J. of Catalysis, 201,22 (2001); Perkas et al., Chem. Comm., 988 (2001); Nikitenko et al.,Angew. Chem. Inter. Ed. (December 2001); Shafi et al., J. Phys. Chem B103, 3358 (1999); Avivi et al., J. Amer. Chem. Soc. 121, 4196 (1999);and Avivi et al., J. Amer. Chem. Soc. 122, 4331 (2000).

Sonication Systems

FIG. 12 shows a general system in which a cellulosic material stream1210 is mixed with a water stream 1212 in a reservoir 1214 to form aprocess stream 1216. A first pump 1218 draws process stream 1216 fromreservoir 1214 and toward a flow cell 1224. Ultrasonic transducer 1226transmits ultrasonic energy into process stream 1216 as the processstream flows through flow cell 1224. A second pump 1230 draws processstream 1216 from flow cell 1224 and toward subsequent processing.

Reservoir 1214 includes a first intake 1232 and a second intake 1234 influid communication with a volume 1236. A conveyor (not shown) deliverscellulosic material stream 1210 to reservoir 1214 through first intake1232. Water stream 1212 enters reservoir 1214 through second intake1234. In some embodiments, water stream 1212 enters volume 1236 along atangent establishing a swirling flow within volume 1236. In certainembodiments, cellulosic material stream 1210 and water stream 1212 areintroduced into volume 1236 along opposing axes to enhance mixing withinthe volume.

Valve 1238 controls the flow of water stream 1212 through second intake1232 to produce a desired ratio of cellulosic material to water (e.g.,approximately 10% cellulosic material, weight by volume). For example,2000 tons/day of cellulosic material can be combined with 1 million to1.5 million gallons/day, e.g., 1.25 million gallons/day, of water.

Mixing of cellulosic material and water in reservoir 1214 is controlledby the size of volume 1236 and the flow rates of cellulosic material andwater into the volume. In some embodiments, volume 1236 is sized tocreate a minimum mixing residence time for the cellulosic material andwater. For example, when 2000 tons/day of cellulosic material and 1.25million gallons/day of water are flowing through reservoir 1214, volume1236 can be about 32,000 gallons to produce a minimum mixing residencetime of about 15 minutes.

Reservoir 1214 includes a mixer 1240 in fluid communication with volume1236. Mixer 1240 agitates the contents of volume 1236 to dispersecellulosic material throughout the water in the volume. For example,mixer 1240 can be a rotating vane disposed in reservoir 1214. In someembodiments, mixer 1240 disperses the cellulosic material substantiallyuniformly throughout the water.

Reservoir 1214 further includes an exit 1242 in fluid communication withvolume 1236 and process stream 1216. The mixture of cellulosic materialand water in volume 1236 flows out of reservoir 1214 via exit 1242. Exit1242 is arranged near the bottom of reservoir 1214 to allow gravity topull the mixture of cellulosic material and water out of reservoir 1214and into process stream 1216.

First pump 1218 (e.g., any of several recessed impeller vortex pumpsmade by Essco Pumps & Controls, Los Angeles, Calif.) moves the contentsof process stream 1216 toward flow cell 1224. In some embodiments, firstpump 1218 agitates the contents of process stream 1216 such that themixture of cellulosic material and water is substantially uniform atinlet 1220 of flow cell 1224. For example, first pump 1218 agitatesprocess stream 1216 to create a turbulent flow that persists along theprocess stream between the first pump and inlet 1220 of flow cell 1224.

Flow cell 1224 includes a reactor volume 1244 in fluid communicationwith inlet 1220 and outlet 1222. In some embodiments, reactor volume1244 is a stainless steel tube capable of withstanding elevatedpressures (e.g., 10 bars). In addition or in the alternative, reactorvolume 1244 includes a rectangular cross section.

Flow cell 1224 further includes a heat exchanger 1246 in thermalcommunication with at least a portion of reactor volume 1244. Coolingfluid 1248 (e.g., water) flows into heat exchanger 1246 and absorbs heatgenerated when process stream 1216 is sonicated in reactor volume 1244.In some embodiments, the flow rate and/or temperature of cooling fluid1248 into heat exchanger 1246 is controlled to maintain an approximatelyconstant temperature in reactor volume 1244. In some embodiments, thetemperature of reactor volume 1244 is maintained at 20 to 50° C., e.g.,25, 30, 35, 40, or 45° C. Additionally or alternatively, heattransferred to cooling fluid 1248 from reactor volume 1244 can be usedin other parts of the overall process.

An adapter section 1226 creates fluid communication between reactorvolume 1244 and a booster 1250 coupled (e.g., mechanically coupled usinga flange) to ultrasonic transducer 1226. For example, adapter section1226 can include a flange and O-ring assembly arranged to create a leaktight connection between reactor volume 1244 and booster 1250. In someembodiments, ultrasonic transducer 1226 is a high-powered ultrasonictransducer made by Hielscher Ultrasonics of Teltow, Germany.

In operation, a generator 1252 delivers electricity to ultrasonictransducer 1252. Ultrasonic transducer 1226 includes a piezoelectricelement that converts the electrical energy into sound in the ultrasonicrange. In some embodiments, the materials are sonicated using soundhaving a frequency of from about 16 kHz to about 110 kHz, e.g., fromabout 18 kHz to about 75 kHz or from about 20 kHz to about 40 kHz.(e.g., sound having a frequency of 20 kHz to 40 kHz).

The ultrasonic energy is then delivered to the working medium throughbooster 1248. The ultrasonic energy traveling through booster 1248 inreactor volume 1244 creates a series of compressions and rarefactions inprocess stream 1216 with an intensity sufficient to create cavitation inprocess stream 1216. Cavitation disaggregates the cellulosic materialdispersed in process stream 1216. Cavitation also produces free radicalsin the water of process stream 1216. These free radicals act to furtherbreak down the cellulosic material in process stream 1216.

In general, 5 to 4000 MJ/m³, e.g., 10, 25, 50, 100, 250, 500, 750, 1000,2000, or 3000 MJ/m³, of ultrasonic energy is applied to process stream16 flowing at a rate of about 0.2 m³/s (about 3200 gallons/min). Afterexposure to ultrasonic energy in reactor volume 1244, process stream1216 exits flow cell 1224 through outlet 1222. Second pump 1230 movesprocess stream 1216 to subsequent processing (e.g., any of severalrecessed impeller vortex pumps made by Essco Pumps & Controls, LosAngeles, Calif.).

While certain embodiments have been described, other embodiments arepossible.

As an example, while process stream 1216 has been described as a singleflow path, other arrangements are possible. In some embodiments forexample, process stream 1216 includes multiple parallel flow paths(e.g., flowing at a rate of 10 gallon/min). In addition or in thealternative, the multiple parallel flow paths of process stream 1216flow into separate flow cells and are sonicated in parallel (e.g., usinga plurality of 16 kW ultrasonic transducers).

As another example, while a single ultrasonic transducer 1226 has beendescribed as being coupled to flow cell 1224, other arrangements arepossible. In some embodiments, a plurality of ultrasonic transducers1226 are arranged in flow cell 1224 (e.g., ten ultrasonic transducerscan be arranged in a flow cell 1224). In some embodiments, the soundwaves generated by each of the plurality of ultrasonic transducers 1226are timed (e.g., synchronized out of phase with one another) to enhancethe cavitation acting upon process stream 1216.

As another example, while a single flow cell 1224 has been described,other arrangements are possible. In some embodiments, second pump 1230moves process stream to a second flow cell where a second booster andultrasonic transducer further sonicate process stream 1216.

As still another example, while reactor volume 1244 has been describedas a closed volume, reactor volume 1244 is open to ambient conditions incertain embodiments. In such embodiments, sonication pretreatment can beperformed substantially simultaneously with other pretreatmenttechniques. For example, ultrasonic energy can be applied to processstream 1216 in reactor volume 1244 while electron beams aresimultaneously introduced into process stream 1216.

As another example, while a flow-through process has been described,other arrangements are possible. In some embodiments, sonication can beperformed in a batch process. For example, a volume can be filled with a10% (weight by volume) mixture of cellulosic material in water andexposed to sound with intensity from about 50 W/cm² to about 600 W/cm²,e.g., from about 75 W/cm² to about 300 W/cm² or from about 95 W/cm² toabout 200 W/cm². Additionally or alternatively, the mixture in thevolume can be sonicated from about 1 hour to about 24 hours, e.g., fromabout 1.5 hours to about 12 hours, or from about 2 hours to about 10hours. In certain embodiments, the material is sonicated for apre-determined time, and then allowed to stand for a secondpre-determined time before sonicating again.

Referring now to FIG. 13, in some embodiments, two electroacoustictransducers are mechanically coupled to a single horn. As shown, a pairof piezoelectric transducers 60 and 62 is coupled to a slotted bar horn64 by respective intermediate coupling horns 70 and 72, the latter alsobeing known as booster horns. The mechanical vibrations provided by thetransducers, responsive to high frequency electrical energy appliedthereto, are transmitted to the respective coupling horns, which may beconstructed to provide a mechanical gain, such as a ratio of 1 to 1.2.The horns are provided with a respective mounting flange 74 and 76 forsupporting the transducer and horn assembly in a stationary housing.

The vibrations transmitted from the transducers through the coupling orbooster horns are coupled to the input surface 78 of the horn and aretransmitted through the horn to the oppositely disposed output surface80, which, during operation, is in forced engagement with a workpiece(not shown) to which the vibrations are applied.

The high frequency electrical energy provided by the power supply 82 isfed to each of the transducers, electrically connected in parallel, viaa balancing transformer 84 and a respective series connected capacitor86 and 90, one capacitor connected in series with the electricalconnection to each of the transducers. The balancing transformer isknown also as “balun” standing for “balancing unit.” The balancingtransformer includes a magnetic core 92 and a pair of identical windings94 and 96, also termed the primary winding and secondary winding,respectively.

In some embodiments, the transducers include commercially availablepiezoelectric transducers, such as Branson Ultrasonics Corporationmodels 105 or 502, each designed for operation at 20 kHz and a maximumpower rating of 3 kW. The energizing voltage for providing maximummotional excursion at the output surface of the transducer is 930 voltrms. The current flow through a transducer may vary between zero and 3.5ampere depending on the load impedance. At 930 volt rms the outputmotion is approximately 20 microns. The maximum difference in terminalvoltage for the same motional amplitude, therefore, can be 186 volt.Such a voltage difference can give rise to large circulating currentsflowing between the transducers. The balancing unit 430 assures abalanced condition by providing equal current flow through thetransducers, hence eliminating the possibility of circulating currents.The wire size of the windings must be selected for the full load currentnoted above and the maximum voltage appearing across a winding input is93 volt.

As an alternative to using ultrasonic energy, high-frequency,rotor-stator devices can be utilized. This type of device produceshigh-shear, microcavitation forces which can disintegrate biomass incontact with such forces. Two commercially available high-frequency,rotor-stator dispersion devices are the Supraton™ devices manufacturedby Krupp Industrietechnik GmbH and marketed by Dorr-Oliver DeutschlandGmbH of Connecticut, and the Dispax™ devices manufactured and marketedby Ika-Works, Inc. of Cincinnati, Ohio. Operation of such amicrocavitation device is discussed in Stuart, U.S. Pat. No. 5,370,999.

While ultrasonic transducer 1226 has been described as including one ormore piezoelectric active elements to create ultrasonic energy, otherarrangements are possible. In some embodiments, ultrasonic transducer1226 includes active elements made of other types of magnetostrictivematerials (e.g., ferrous metals). Design and operation of such ahigh-powered ultrasonic transducer is discussed in Hansen et al., U.S.Pat. No. 6,624,539. In some embodiments, ultrasonic energy istransferred to process stream 16 through an electrohydraulic system.

While ultrasonic transducer 1226 has been described as using theelectromagnetic response of magnetorestrictive materials to produceultrasonic energy, other arrangements are possible. In some embodiments,acoustic energy in the form of an intense shock wave can be applieddirectly to process stream 16 using an underwater spark. In someembodiments, ultrasonic energy is transferred to process stream 16through a thermohydraulic system. For example, acoustic waves of highenergy density can be produced by applying power across an enclosedvolume of electrolyte, thereby heating the enclosed volume and producinga pressure rise that is subsequently transmitted through a soundpropagation medium (e.g., process stream 1216). Design and operation ofsuch a thermohydraulic transducer is discussed in Hartmann et al., U.S.Pat. No. 6,383,152.

Pyrolysis

One or more pyrolysis processing sequences can be used to process rawfeedstock from a wide variety of different sources to extract usefulsubstances from the feedstock, and to provide partially degraded organicmaterial which functions as input to further processing steps and/orsequences.

Referring again to the general schematic in FIG. 8, a first material 2that includes cellulose having a first number average molecular weight(^(T)M_(N2)) is pyrolyzed, e.g., by heating the first material in a tubefurnace, to provide a second material 3 that includes cellulose having asecond number average molecular weight (^(T)M_(N2)) lower than the firstnumber average molecular weight. The second material (or the first andsecond material in certain embodiments) is/are combined with amicroorganism (e.g., a bacterium or a yeast) that can utilize the secondand/or first material to produce a fuel 5 that is or includes hydrogen,an alcohol (e.g., ethanol or butanol, such as n-, sec or t-butanol), anorganic acid, a hydrocarbon or mixtures of any of these.

Since the second material has cellulose having a reduced molecularweight relative to the first material, and in some instances, a reducedcrystallinity as well, the second material is generally moredispersible, swellable and/or soluble in a solution containing themicroorganism, e.g., at a concentration of greater than 10⁶microorganisms/mL. These properties make the second material 3 moresusceptible to chemical, enzymatic and/or microbial attack relative tothe first material 2, which can greatly improve the production rateand/or production level of a desired product, e.g., ethanol. Pyrolysiscan also sterilize the first and second materials.

In some embodiments, the second number average molecular weight(^(T)M_(N2)) is lower than the first number average molecular weight(^(T)M_(N2)) by more than about 10 percent, e.g., 15, 20, 25, 30, 35,40, 50 percent, 60 percent, or even more than about 75 percent.

In some instances, the second material has cellulose that has ascrystallinity (^(T)C₂) that is lower than the crystallinity (^(T)C₁) ofthe cellulose of the first material. For example, (^(T)C₂) can be lowerthan (^(T)C₁) by more than about 10 percent, e.g., 15, 20, 25, 30, 35,40, or even more than about 50 percent.

In some embodiments, the starting crystallinity (prior to pyrolysis) isfrom about 40 to about 87.5 percent, e.g., from about 50 to about 75percent or from about 60 to about 70 percent, and the crystallinityindex after pyrolysis is from about 10 to about 50 percent, e.g., fromabout 15 to about 45 percent or from about 20 to about 40 percent.However, in certain embodiments, e.g., after extensive pyrolysis, it ispossible to have a crystallinity index of lower than 5 percent. In someembodiments, the material after pyrolysis is substantially amorphous.

In some embodiments, the starting number average molecular weight (priorto pyrolysis) is from about 200,000 to about 3,200,000, e.g., from about250,000 to about 1,000,000 or from about 250,000 to about 700,000, andthe number average molecular weight after pyrolysis is from about 50,000to about 200,000, e.g., from about 60,000 to about 150,000 or from about70,000 to about 125,000. However, in some embodiments, e.g., afterextensive pyrolysis, it is possible to have a number average molecularweight of less than about 10,000 or even less than about 5,000.

In some embodiments, the second material can have a level of oxidation(^(T)O₂) that is higher than the level of oxidation (^(T)O₁) of thefirst material. A higher level of oxidation of the material can aid inits dispersability, swellability and/or solubility, further enhancingthe materials susceptibility to chemical, enzymatic or microbial attack.In some embodiments, to increase the level of the oxidation of thesecond material relative to the first material, the pyrolysis isperformed in an oxidizing environment, producing a second material thatis more oxidized than the first material. For example, the secondmaterial can have more hydroxyl groups, aldehyde groups, ketone groups,ester groups or carboxylic acid groups, which can increase itshydrophilicity.

In some embodiments, the pyrolysis of the materials is continuous. Inother embodiments, the material is pyrolyzed for a pre-determined time,and then allowed to cool for a second pre-determined time beforepyrolyzing again.

Pyrolysis Systems

FIG. 14 shows a process flow diagram 6000 that includes various steps ina pyrolytic feedstock pretreatment system. In first step 6010, a supplyof dry feedstock is received from a feed source.

As described above, the dry feedstock from the feed source may bepre-processed prior to delivery to the pyrolysis chamber. For example,if the feedstock is derived from plant sources, certain portions of theplant material may be removed prior to collection of the plant materialand/or before the plant material is delivered by the feedstock transportdevice. Alternatively, or in addition, the biomass feedstock can besubjected to mechanical processing 6020 (e.g., to reduce the averagelength of fibers in the feedstock) prior to delivery to the pyrolysischamber.

Following mechanical processing, the feedstock undergoes a moistureadjustment step 6030. The nature of the moisture adjustment step dependsupon the moisture content of the mechanically processed feedstock.Typically, pyrolysis of feedstock occurs most efficiently when themoisture content of the feedstock is between about 10% and about 30%(e.g., between 15% and 25%) by weight of the feedstock. If the moisturecontent of the feedstock is larger than about 40% by weight, the extrathermal load presented by the water content of the feedstock increasesthe energy consumption of subsequent pyrolysis steps.

In some embodiments, if the feedstock has a moisture content which islarger than about 30% by weight, drier feedstock material 6220 which hasa low moisture content can be blended in, creating a feedstock mixturein step 6030 with an average moisture content that is within the limitsdiscussed above. In certain embodiments, feedstock with a high moisturecontent can simply be dried by dispersing the feedstock material on amoving conveyor that cycles the feedstock through an in-line heatingunit. The heating unit evaporates a portion of the water present in thefeedstock.

In some embodiments, if the feedstock from step 6020 has a moisturecontent which is too low (e.g., lower than about 10% by weight), themechanically processed feedstock can be combined with wetter feedstockmaterial 6230 with a higher moisture content, such as sewage sludge.Alternatively, or in addition, water 6240 can be added to the dryfeedstock from step 6020 to increase its moisture content.

In step 6040, the feedstock—now with its moisture content adjusted tofall within suitable limits—can be preheated in an optional preheatingstep 6040. Preheating step 6040 can be used to increase the temperatureof the feedstock to between 75° C. and 150° C. in preparation forsubsequent pyrolysis of the feedstock. Depending upon the nature of thefeedstock and the particular design of the pyrolysis chamber, preheatingthe feedstock can ensure that heat distribution within the feedstockremains more uniform during pyrolysis, and can reduce the thermal loadon the pyrolysis chamber.

The feedstock is then transported to a pyrolysis chamber to undergopyrolysis in step 6050. In some embodiments, transport of the feedstockis assisted by adding one or more pressurized gases 6210 to thefeedstock stream. The gases create a pressure gradient in a feedstocktransport conduit, propelling the feedstock into the pyrolysis chamber(and even through the pyrolysis chamber). In certain embodiments,transport of the feedstock occurs mechanically; that is, a transportsystem that includes a conveyor such as an auger transports thefeedstock to the pyrolysis chamber.

Other gases 6210 can also be added to the feedstock prior to thepyrolysis chamber. In some embodiments, for example, one or morecatalyst gases can be added to the feedstock to assist decomposition ofthe feedstock during pyrolysis. In certain embodiments, one or morescavenging agents can be added to the feedstock to trap volatilematerials released during pyrolysis. For example, various sulfur-basedcompounds such as sulfides can be liberated during pyrolysis, and anagent such as hydrogen gas can be added to the feedstock to causedesulfurization of the pyrolysis products. Hydrogen combines withsulfides to form hydrogen sulfide gas, which can be removed from thepyrolyzed feedstock.

Pyrolysis of the feedstock within the chamber can include heating thefeedstock to relatively high temperatures to cause partial decompositionof the feedstock. Typically, the feedstock is heated to a temperature ina range from 150° C. to 1100° C. The temperature to which the feedstockis heated depends upon a number of factors, including the composition ofthe feedstock, the feedstock average particle size, the moisturecontent, and the desired pyrolysis products. For many types of biomassfeedstock, for example, pyrolysis temperatures between 300° C. and 550°C. are used.

The residence time of the feedstock within the pyrolysis chambergenerally depends upon a number of factors, including the pyrolysistemperature, the composition of the feedstock, the feedstock averageparticle size, the moisture content, and the desired pyrolysis products.In some embodiments, feedstock materials are pyrolyzed at a temperaturejust above the decomposition temperature for the material in an inertatmosphere, e.g., from about 2° C. above to about 10° C. above thedecomposition temperature or from about 3° C. above to about 7° C. abovethe decomposition temperature. In such embodiments, the material isgenerally kept at this temperature for greater than 0.5 hours, e.g.,greater than 1.0 hours or greater than about 2.0 hours. In otherembodiments, the materials are pyrolyzed at a temperature well above thedecomposition temperature for the material in an inert atmosphere, e.g.,from about 75° C. above to about 175° C. above the decompositiontemperature or from about 85° C. above to about 150° C. above thedecomposition temperature. In such embodiments, the material isgenerally kept at this temperature for less than 0.5 hour, e.g., less 20minutes, less than 10 minutes, less than 5 minutes or less than 2minutes. In still other embodiments, the materials are pyrolyzed at anextreme temperature, e.g., from about 200° C. above to about 500° C.above the decomposition temperature of the material in an inertenvironment or from about 250° C. above to about 400° C. above thedecomposition temperature. In such embodiments, the material usgenerally kept at this temperature for less than 1 minute, e.g., lessthan 30 seconds, less than 15 seconds, less than 10 seconds, less than 5seconds, less than 1 second or less than 500 ms. Such embodiments aretypically referred to as flash pyrolysis.

In some embodiments, the feedstock is heated relatively rapidly to theselected pyrolysis temperature within the chamber. For example, thechamber can be designed to heat the feedstock at a rate of between 500°C./s and 11,000° C./s, for example from 500° C./s to 1000° C./s.

A turbulent flow of feedstock material within the pyrolysis chamber isusually advantageous, as it ensures relatively efficient heat transferto the feedstock material from the heating sub-system. Turbulent flowcan be achieved, for example, by blowing the feedstock material throughthe chamber using one or more injected carrier gases 6210. In general,the carrier gases are relatively inert towards the feedstock material,even at the high temperatures in the pyrolysis chamber. Exemplarycarrier gases include, for example, nitrogen, argon, methane, carbonmonoxide, and carbon dioxide. Alternatively, or in addition, mechanicaltransport systems such as augers can transport and circulate thefeedstock within the pyrolysis chamber to create a turbulent feedstockflow.

In some embodiments, pyrolysis of the feedstock occurs substantially inthe absence of oxygen and other reactive gases. Oxygen can be removedfrom the pyrolysis chamber by periodic purging of the chamber with highpressure nitrogen (e.g., at nitrogen pressures of 2 bar or more).Following purging of the chamber, a gas mixture present in the pyrolysischamber (e.g., during pyrolysis of the feedstock) can include less than4 mole % oxygen (e.g., less than 1 mole % oxygen, and even less than 0.5mole % oxygen). The absence of oxygen ensures that ignition of thefeedstock does not occur at the elevated pyrolysis temperatures.

In certain embodiments, relatively small amounts of oxygen can beintroduced into the feedstock and are present during pyrolysis. Thistechnique is referred to as oxidative pyrolysis. Typically, oxidativepyrolysis occurs in multiple heating stages. For example, in a firstheating stage, the feedstock is heated in the presence of oxygen tocause partial oxidation of the feedstock. This stage consumes theavailable oxygen in the pyrolysis chamber. Then, in subsequent heatingstages, the feedstock temperature is further elevated. With all of theoxygen in the chamber consumed, however, feedstock combustion does notoccur, and combustion-free pyrolytic decomposition of the feedstock(e.g., to generate hydrocarbon products) occurs. In general, the processof heating feedstock in the pyrolysis chamber to initiate decompositionis endothermic. However, in oxidative pyrolysis, formation of carbondioxide by oxidation of the feedstock is an exothermic process. The heatreleased from carbon dioxide formation can assist further pyrolysisheating stages, thereby lessening the thermal load presented by thefeedstock.

In some embodiments, pyrolysis occurs in an inert environment, such aswhile feedstock materials are bathed in argon or nitrogen gas. Incertain embodiments, pyrolysis can occur in an oxidizing environment,such as in air or argon enriched in air. In some embodiments, pyrolysiscan take place in a reducing environment, such as while feedstockmaterials are bathed in hydrogen gas. To aid pyrolysis, various chemicalagents, such as oxidants, reductants, acids or bases can be added to thematerial prior to or during pyrolysis. For example, sulfuric acid can beadded, or a peroxide (e.g., benzoyl peroxide) can be added.

As discussed above, a variety of different processing conditions can beused, depending upon factors such as the feedstock composition and thedesired pyrolysis products. For example, for cellulose-containingfeedstock material, relatively mild pyrolysis conditions can beemployed, including flash pyrolysis temperatures between 375° C. and450° C., and residence times of less than 1 second. As another example,for organic solid waste material such as sewage sludge, flash pyrolysistemperatures between 500° C. and 650° C. are typically used, withresidence times of between 0.5 and 3 seconds. In general, many of thepyrolysis process parameters, including residence time, pyrolysistemperature, feedstock turbulence, moisture content, feedstockcomposition, pyrolysis product composition, and additive gas compositioncan be regulated automatically by a system of regulators and anautomated control system.

Following pyrolysis step 6050, the pyrolysis products undergo aquenching step 6250 to reduce the temperature of the products prior tofurther processing. Typically, quenching step 6250 includes spraying thepyrolysis products with streams of cooling water 6260. The cooling wateralso forms a slurry that includes solid, undissolved product materialand various dissolved products. Also present in the product stream is amixture that includes various gases, including product gases, carriergases, and other types of process gases.

The product stream is transported via in-line piping to a gas separatorthat performs a gas separation step 6060, in which product gases andother gases are separated from the slurry formed by quenching thepyrolysis products. The separated gas mixture is optionally directed toa blower 6130, which increases the gas pressure by blowing air into themixture. The gas mixture can be subjected to a filtration step 6140, inwhich the gas mixture passes through one or more filters (e.g.,activated charcoal filters) to remove particulates and other impurities.In a subsequent step 6150, the filtered gas can be compressed and storedfor further use. Alternatively, the filtered gas can be subjected tofurther processing steps 6160. For example, in some embodiments, thefiltered gas can be condensed to separate different gaseous compoundswithin the gas mixture. The different compounds can include, forexample, various hydrocarbon products (e.g., alcohols, alkanes, alkenes,alkynes, ethers) produced during pyrolysis. In certain embodiments, thefiltered gas containing a mixture of hydrocarbon components can becombined with steam gas 6170 (e.g., a mixture of water vapor and oxygen)and subjected to a cracking process to reduce molecular weights of thehydrocarbon components.

In some embodiments, the pyrolysis chamber includes heat sources thatburn hydrocarbon gases such as methane, propane, and/or butane to heatthe feedstock. A portion 6270 of the separated gases can be recirculatedinto the pyrolysis chamber for combustion, to generate process heat tosustain the pyrolysis process.

In certain embodiments, the pyrolysis chamber can receive process heatthat can be used to increase the temperature of feedstock materials. Forexample, irradiating feedstock with radiation (e.g., gamma radiation,electron beam radiation, or other types of radiation) can heat thefeedstock materials to relatively high temperatures. The heatedfeedstock materials can be cooled by a heat exchange system that removessome of the excess heat from the irradiated feedstock. The heat exchangesystem can be configured to transport some of the heat energy to thepyrolysis chamber to heat (or pre-heat) feedstock material, therebyreducing energy cost for the pyrolysis process.

The slurry containing liquid and solid pyrolysis products can undergo anoptional de-watering step 6070, in which excess water can be removedfrom the slurry via processes such as mechanical pressing andevaporation. The excess water 6280 can be filtered and then recirculatedfor further use in quenching the pyrolysis decomposition products instep 6250.

The de-watered slurry then undergoes a mechanical separation step 6080,in which solid product material 6110 is separated from liquid productmaterial 6090 by a series of increasingly-fine filters. In step 6100,the liquid product material 6090 can then be condensed (e.g., viaevaporation) to remove waste water 6190, and purified by processes suchas extraction. Extraction can include the addition of one or moreorganic solvents 6180, for example, to separate products such as oilsfrom products such as alcohols. Suitable organic solvents include, forexample, various hydrocarbons and halo-hydrocarbons. The purified liquidproducts 6200 can then be subjected to further processing steps. Wastewater 6190 can be filtered if necessary, and recirculated for furtheruse in quenching the pyrolysis decomposition products in step 6250.

After separation in step 6080, the solid product material 6110 isoptionally subjected to a drying step 6120 that can include evaporationof water. Solid material 6110 can then be stored for later use, orsubjected to further processing steps, as appropriate.

The pyrolysis process parameters discussed above are exemplary. Ingeneral, values of these parameters can vary widely according to thenature of the feedstock and the desired products. Moreover, a widevariety of different pyrolysis techniques, including using heat sourcessuch as hydrocarbon flames and/or furnaces, infrared lasers, microwaveheaters, induction heaters, resistive heaters, and other heating devicesand configurations can be used.

A wide variety of different pyrolysis chambers can be used to decomposethe feedstock. In some embodiments, for example, pyrolyzing feedstockcan include heating the material using a resistive heating member, suchas a metal filament or metal ribbon. The heating can occur by directcontact between the resistive heating member and the material.

In certain embodiments, pyrolyzing can include heating the material byinduction, such as by using a Currie-Point pyrolyzer. In someembodiments, pyrolyzing can include heating the material by theapplication of radiation, such as infrared radiation. The radiation canbe generated by a laser, such as an infrared laser.

In certain embodiments, pyrolyzing can include heating the material witha convective heat. The convective heat can be generated by a flowingstream of heated gas. The heated gas can be maintained at a temperatureof less than about 1200° C., such as less than 1000° C., less than 750°C., less than 600° C., less than 400° C. or even less than 300° C. Theheated gas can be maintained at a temperature of greater than about 250°C. The convective heat can be generated by a hot body surrounding thefirst material, such as in a furnace.

In some embodiments, pyrolyzing can include heating the material withsteam at a temperature above about 250° C.

An embodiment of a pyrolysis chamber is shown in FIG. 15. Chamber 6500includes an insulated chamber wall 6510 with a vent 6600 for exhaustgases, a plurality of burners 6520 that generate heat for the pyrolysisprocess, a transport duct 6530 for transporting the feedstock throughchamber 6500, augers 6590 for moving the feedstock through duct 6530 ina turbulent flow, and a quenching system 6540 that includes an auger6610 for moving the pyrolysis products, water jets 6550 for spraying thepyrolysis products with cooling water, and a gas separator forseparating gaseous products 6580 from a slurry 6570 containing solid andliquid products.

Another embodiment of a pyrolysis chamber is shown in FIG. 16. Chamber6700 includes an insulated chamber wall 6710, a feedstock supply duct6720, a sloped inner chamber wall 6730, burners 6740 that generate heatfor the pyrolysis process, a vent 6750 for exhaust gases, and a gasseparator 6760 for separating gaseous products 6770 from liquid andsolid products 6780. Chamber 6700 is configured to rotate in thedirection shown by arrow 6790 to ensure adequate mixing and turbulentflow of the feedstock within the chamber.

A further embodiment of a pyrolysis chamber is shown in FIG. 17.Filament pyrolyzer 1712 includes a sample holder 1713 with resistiveheating element 1714 in the form of a wire winding through the openspace defined by the sample holder 1713. Optionally, the heated elementcan be spun about axis 1715 (as indicated by arrow 1716) to tumble thematerial that includes the cellulosic material in sample holder 1713.The space 1718 defined by enclosure 1719 is maintained at a temperatureabove room temperature, e.g., 200 to 250° C. In a typical usage, acarrier gas, e.g., an inert gas, or an oxidizing or reducing gas,traverses through the sample holder 1713 while the resistive heatingelement is rotated and heated to a desired temperature, e.g., 325° C.After an appropriate time, e.g., 5 to 10 minutes, the pyrolyzed materialis emptied from the sample holder. The system shown in FIG. 17 can bescaled and made continuous. For example, rather than a wire as theheating member, the heating member can be an auger screw. Material cancontinuously fall into the sample holder, striking a heated screw thatpyrolizes the material. At the same time, the screw can push thepyrolyzed material out of the sample holder to allow for the entry offresh, unpyrolyzed material.

Another embodiment of a pyrolysis chamber is shown in FIG. 18, whichfeatures a Curie-Point pyrolyzer 1820 that includes a sample chamber1821 housing a ferromagnetic foil 1822. Surrounding the sample chamber1821 is an RF coil 1823. The space 1824 defined by enclosure 1825 ismaintained at a temperature above room temperature, e.g., 200 to 250° C.In a typical usage, a carrier gas traverses through the sample chamber1821 while the foil 1822 is inductively heated by an applied RF field topyrolize the material at a desired temperature.

Yet another embodiment of a pyrolysis chamber is shown in FIG. 19.Furnace pyrolyzer 130 includes a movable sample holder 131 and a furnace132. In a typical usage, the sample is lowered (as indicated by arrow137) into a hot zone 135 of furnace 132, while a carrier gas fills thehousing 136 and traverses through the sample holder 131. The sample isheated to the desired temperature for a desired time to provide apyrolyzed product. The pyrolyzed product is removed from the pyrolyzerby raising the sample holder (as indicated by arrow 134).

In certain embodiments, as shown in FIG. 20, a cellulosic target 140 canbe pyrolyzed by treating the target, which is housed in a vacuum chamber141, with laser light, e.g., light having a wavelength of from about 225nm to about 1500 nm. For example, the target can be ablated at 266 nm,using the fourth harmonic of a Nd-YAG laser (Spectra Physics, GCR170,San Jose, Calif.). The optical configuration shown allows the nearlymonochromatic light 143 generated by the laser 142 to be directed usingmirrors 144 and 145 onto the target after passing though a lens 146 inthe vacuum chamber 141. Typically, the pressure in the vacuum chamber ismaintained at less than about 10⁻⁶ mm Hg. In some embodiments, infraredradiation is used, e.g., 1.06 micron radiation from a Nd-YAG laser. Insuch embodiments, a infrared sensitive dye can be combined with thecellulosic material to produce a cellulosic target. The infrared dye canenhance the heating of the cellulosic material. Laser ablation isdescribed by Blanchet-Fincher et al. in U.S. Pat. No. 5,942,649.

Referring to FIG. 21, in some embodiments, a cellulosic material can beflash pyrolyzed by coating a tungsten filament 150, such as a 5 to 25mil tungsten filament, with the desired cellulosic material while thematerial is housed in a vacuum chamber 151. To affect pyrolysis, currentis passed through the filament, which causes a rapid heating of thefilament for a desired time. Typically, the heating is continued forseconds before allowing the filament to cool. In some embodiments, theheating is performed a number of times to effect the desired amount ofpyrolysis.

In certain embodiments, carbohydrate-containing biomass material can beheated in an absence of oxygen in a fluidized bed reactor. If desired,the carbohydrate containing biomass can have relatively thincross-sections, and can include any of the fibrous materials describedherein, for efficient heat transfer. The material can be heated bythermal transfer from a hot metal or ceramic, such as glass beads orsand in the reactor, and the resulting pyrolysis liquid or oil can betransported to a central refinery for making combustible fuels or otheruseful products.

Oxidation

One or more oxidative processing sequences can be used to process rawfeedstock from a wide variety of different sources to extract usefulsubstances from the feedstock, and to provide partially degraded organicmaterial which functions as input to further processing steps and/orsequences.

Referring again to FIG. 8, a first material 2 that includes cellulosehaving a first number average molecular weight (^(T)M_(N2)) and having afirst oxygen content (^(T)O₁) is oxidized, e.g., by heating the firstmaterial in a tube furnace in stream of air or oxygen-enriched air, toprovide a second material 3 that includes cellulose having a secondnumber average molecular weight (^(T)M_(N2)) and having a second oxygencontent (^(T)O₂) higher than the first oxygen content (^(T)O₁). Thesecond material (or the first and second material in certainembodiments) can be, e.g., combined with a resin, such as a moltenthermoplastic resin or a microorganism, to provide a composite 4 havingdesirable mechanical properties, or a fuel 5. Providing a higher levelof oxidation can improve dispersability of the oxidized material in aresin and can also improve the interfacial bond between the oxidizedmaterial and the resin. Improved dispersability and/or interfacialbonding (in some instances in combination with maintaining molecularweight) can provide composites with exceptional mechanical properties,such as improved abrasion resistance, compression strength, fractureresistance, impact strength, bending strength, tensile modulus, flexuralmodulus and elongation at break.

Such materials can also be combined with a solid and/or a liquid. Forexample, the liquid can be in the form of a solution and the solid canbe particulate in form. The liquid and/or solid can include amicroorganism, e.g., a bacterium, and/or an enzyme. For example, thebacterium and/or enzyme can work on the cellulosic or lignocellulosicmaterial to produce a fuel, such as ethanol, or a coproduct, such as aprotein. Fuels and coproducts are described in “FIBROUS MATERIALS ANDCOMPOSITES,” U.S. Ser. No. 11/453,951, filed Jun. 15, 2006. The entirecontents of each of the foregoing applications are incorporated hereinby reference.

In some embodiments, the second number average molecular weight is notmore 97 percent lower than the first number average molecular weight,e.g., not more than 95 percent, 90, 85, 80, 75, 70, 65, 60, 55, 50, 45,40, 30, 20, 12.5, 10.0, 7.5, 5.0, 4.0, 3.0, 2.5, 2.0 or not more than1.0 percent lower than the first number average molecular weight. Theamount of reduction of molecular weight will depend upon theapplication. For example, in some preferred embodiments that providecomposites, the second number average molecular weight is substantiallythe same as the first number average molecular weight. In otherapplications, such as making ethanol or another fuel or coproduct, ahigher amount of molecular weight reduction is generally preferred.

For example, in some embodiments that provide a composite, the startingnumber average molecular weight (prior to oxidation) is from about200,000 to about 3,200,000, e.g., from about 250,000 to about 1,000,000or from about 250,000 to about 700,000, and the number average molecularweight after oxidation is from about 175,000 to about 3,000,000, e.g.,from about 200,000 to about 750,000 or from about 225,000 to about600,000.

Resins utilized can be thermosets or thermoplastics. Examples ofthermoplastic resins include rigid and elastomeric thermoplastics. Rigidthermoplastics include polyolefins (e.g., polyethylene, polypropylene,or polyolefin copolymers), polyesters (e.g., polyethyleneterephthalate), polyamides (e.g., nylon 6, 6/12 or 6/10), andpolyethyleneimines. Examples of elastomeric thermoplastic resins includeelastomeric styrenic copolymers (e.g., styrene-ethylene-butylene-styrenecopolymers), polyamide elastomers (e.g., polyether-polyamide copolymers)and ethylene-vinyl acetate copolymer.

In particular embodiments, lignin is utilized, e.g., any lignin that isgenerated in any process described herein.

In some embodiments, the thermoplastic resin has a melt flow rate ofbetween 10 g/10 minutes to 60 g/10 minutes, e.g., between 20 g/10minutes to 50 g/10 minutes, or between 30 g/10 minutes to 45 g/10minutes, as measured using ASTM 1238. In certain embodiments, compatibleblends of any of the above thermoplastic resins can be used.

In some embodiments, the thermoplastic resin has a polydispersity index(PDI), i.e., a ratio of the weight average molecular weight to thenumber average molecular weight, of greater than 1.5, e.g., greater than2.0, greater than 2.5, greater than 5.0, greater than 7.5, or evengreater than 10.0.

In specific embodiments, polyolefins or blends of polyolefins areutilized as the thermoplastic resin.

Examples of thermosetting resins include natural rubber,butadiene-rubber and polyurethanes.

In some embodiments in which the materials are used to make a fuel or acoproduct, the starting number average molecular weight (prior tooxidation) is from about 200,000 to about 3,200,000, e.g., from about250,000 to about 1,000,000 or from about 250,000 to about 700,000, andthe number average molecular weight after oxidation is from about 50,000to about 200,000, e.g., from about 60,000 to about 150,000 or from about70,000 to about 125,000. However, in some embodiments, e.g., afterextensive oxidation, it is possible to have a number average molecularweight of less than about 10,000 or even less than about 5,000.

In some embodiments, the second oxygen content is at least about fivepercent higher than the first oxygen content, e.g., 7.5 percent higher,10.0 percent higher, 12.5 percent higher, 15.0 percent higher or 17.5percent higher. In some preferred embodiments, the second oxygen contentis at least about 20.0 percent higher than the oxygen content of thefirst material. Oxygen content is measured by elemental analysis bypyrolyzing a sample in a furnace operating 1300° C. or higher. Asuitable elemental analyzer is the LECO CHNS-932 analyzer with a VTF-900high temperature pyrolysis furnace.

In some embodiments, oxidation of first material 200 does not result ina substantial change in the crystallinity of the cellulose. However, insome instances, e.g., after extreme oxidation, the second material hascellulose that has as crystallinity (^(T)C₂) that is lower than thecrystallinity (^(T)C₁) of the cellulose of the first material. Forexample, (^(T)C₂) can be lower than (^(T)C₁) by more than about 5percent, e.g., 10, 15, 20, or even 25 percent. This can be desirablewhen optimizing the flexural fatigue properties of the composite is agoal. For example, reducing the crystallinity can improve the elongationat break or can enhance the impact resistance of a composite. This canalso be desirable to enhance solubility of the materials in a liquid,such as a liquid that includes a bacterium and/or an enzyme.

In some embodiments, the starting crystallinity index (prior tooxidation) is from about 40 to about 87.5 percent, e.g., from about 50to about 75 percent or from about 60 to about 70 percent, and thecrystallinity index after oxidation is from about 30 to about 75.0percent, e.g., from about 35.0 to about 70.0 percent or from about 37.5to about 65.0 percent. However, in certain embodiments, e.g., afterextensive oxidation, it is possible to have a crystallinity index oflower than 5 percent. In some embodiments, the material after oxidationis substantially amorphous.

Without wishing to be bound by any particular theory, it is believedthat oxidation increases the number of hydrogen-bonding groups on thecellulose, such as hydroxyl groups, aldehyde groups, ketone groupscarboxylic acid groups or anhydride groups, which can increase itsdispersability and/or its solubility (e.g., in a liquid). To furtherimprove dispersability in a resin, the resin can include a componentthat includes hydrogen-bonding groups, such as one or more anhydridegroups, carboxylic acid groups, hydroxyl groups, amide groups, aminegroups or mixtures of any of these groups. In some preferredembodiments, the component includes a polymer copolymerized with and/orgrafted with maleic anhydride. Such materials are available from DuPontunder the tradename FUSABOND®.

Generally, oxidation of first material 200 occurs in an oxidizingenvironment. For example, the oxidation can be effected or aided bypyrolysis in an oxidizing environment, such as in air or argon enrichedin air. To aid in the oxidation, various chemical agents, such asoxidants, acids or bases can be added to the material prior to or duringoxidation. For example, a peroxide (e.g., benzoyl peroxide) can be addedprior to oxidation.

Oxidation Systems

FIG. 22 shows a process flow diagram 5000 that includes various steps inan oxidative feedstock pretreatment system. In first step 5010, a supplyof dry feedstock is received from a feed source. The feed source caninclude, for example, a storage bed or container that is connected to anin-line oxidation reactor via a conveyor belt or another feedstocktransport device.

As described above, the dry feedstock from the feed source may bepre-processed prior to delivery to the oxidation reactor. For example,if the feedstock is derived from plant sources, certain portions of theplant material may be removed prior to collection of the plant materialand/or before the plant material is delivered by the feedstock transportdevice. Alternatively, or in addition, the biomass feedstock can besubjected to mechanical processing (e.g., to reduce the average lengthof fibers in the feedstock) prior to delivery to the oxidation reactor.

Following mechanical processing 5020, feedstock 5030 is transported to amixing system which introduces water 5150 into the feedstock in amechanical mixing process. Combining water with the processed feedstockin mixing step 5040 creates an aqueous feedstock slurry 5050 which canthen be treated with one or more oxidizing agents.

Typically, one liter of water is added to the mixture for every 0.02 kgto 1.0 kg of dry feedstock. The ratio of feedstock to water in themixture depends upon the source of the feedstock and the specificoxidizing agents used further downstream in the overall process. Forexample, in typical industrial processing sequences for lignocellulosicbiomass, aqueous feedstock slurry 5050 includes from about 0.5 kg toabout 1.0 kg of dry biomass per liter of water.

In some embodiments, one or more fiber-protecting additives 5170 canalso be added to the feedstock slurry in feedstock mixing step 5040.Fiber-protecting additives help to reduce degradation of certain typesof biomass fibers (e.g., cellulose fibers) during oxidation of thefeedstock. Fiber-protecting additives can be used, for example, if adesired product from processing a lignocellulosic feedstock includescellulose fibers. Exemplary fiber-protecting additives include magnesiumcompounds such as magnesium hydroxide. Concentrations offiber-protecting additives in feedstock slurry 5050 can be from 0.1% to0.4% of the dry weight of the biomass feedstock, for example.

In certain embodiments, aqueous feedstock slurry 5050 can be subjectedto an optional extraction 5180 with an organic solvent to removewater-insoluble substances from the slurry. For example, extraction ofslurry 5050 with one or more organic solvents yields a purified slurryand an organic waste stream 5210 that includes water-insoluble materialssuch as fats, oils, and other non-polar, hydrocarbon-based substances.Suitable solvents for performing extraction of slurry 5050 includevarious alcohols, hydrocarbons, and halo-hydrocarbons, for example.

In some embodiments, aqueous feedstock slurry 5050 can be subjected toan optional thermal treatment 5190 to further prepare the feedstock foroxidation. An example of a thermal treatment includes heating thefeedstock slurry in the presence of pressurized steam. In fibrousbiomass feedstock, the pressurized steam swells the fibers, exposing alarger fraction of fiber surfaces to the aqueous solvent and tooxidizing agents that are introduced in subsequent processing steps.

In certain embodiments, aqueous feedstock slurry 5050 can be subjectedto an optional treatment with basic agents 5200. Treatment with one ormore basic agents can help to separate lignin from cellulose inlignocellulosic biomass feedstock, thereby improving subsequentoxidation of the feedstock. Exemplary basic agents include alkali andalkaline earth hydroxides such as sodium hydroxide, potassium hydroxide,and calcium hydroxide. In general, a variety of basic agents can beused, typically in concentrations from about 0.01% to about 0.5% of thedry weight of the feedstock.

Aqueous feedstock slurry 5050 is transported (e.g., by an in-line pipingsystem) to a chamber, which can be an oxidation preprocessing chamber oran oxidation reactor. In oxidation preprocessing step 5060, one or moreoxidizing agents 5160 are added to feedstock slurry 5050 to form anoxidizing medium. In some embodiments, for example, oxidizing agents5160 can include hydrogen peroxide. Hydrogen peroxide can be added toslurry 5050 as an aqueous solution, and in proportions ranging from 3%to between 30% and 35% by weight of slurry 5050. Hydrogen peroxide has anumber of advantages as an oxidizing agent. For example, aqueoushydrogen peroxide solution is relatively inexpensive, is relativelychemically stable, and is not particularly hazardous relative to otheroxidizing agents (and therefore does not require burdensome handlingprocedures and expensive safety equipment). Moreover, hydrogen peroxidedecomposes to form water during oxidation of feedstock, so that wastestream cleanup is relatively straightforward and inexpensive.

In certain embodiments, oxidizing agents 5160 can include oxygen (e.g.,oxygen gas) either alone, or in combination with hydrogen peroxide.Oxygen gas can be bubbled into slurry 5050 in proportions ranging from0.5% to 10% by weight of slurry 5050. Alternatively, or in addition,oxygen gas can also be introduced into a gaseous phase in equilibriumwith slurry 5050 (e.g., a vapor head above slurry 5050). The oxygen gascan be introduced into either an oxidation preprocessing chamber or intoan oxidation reactor (or into both), depending upon the configuration ofthe oxidative processing system. Typically, for example, the partialpressure of oxygen in the vapor above slurry 5050 is larger than theambient pressure of oxygen, and ranges from 0.5 bar to 35 bar, dependingupon the nature of the feedstock.

The oxygen gas can be introduced in pure form, or can be mixed with oneor more carrier gases. For example, in some embodiments, high-pressureair provides the oxygen in the vapor. In certain embodiments, oxygen gascan be supplied continuously to the vapor phase to ensure that aconcentration of oxygen in the vapor remains within certainpredetermined limits during processing of the feedstock. In someembodiments, oxygen gas can be introduced initially in sufficientconcentration to oxidize the feedstock, and then the feedstock can betransported to a closed, pressurized vessel (e.g., an oxidation reactor)for processing.

In certain embodiments, oxidizing agents 5160 can include nascent oxygen(e.g., oxygen radicals). Typically, nascent oxygen is produced as neededin an oxidation reactor or in a chamber in fluid communication with anoxidation reactor by one or more decomposition reactions. For example,in some embodiments, nascent oxygen can be produced from a reactionbetween NO and O₂ in a gas mixture or in solution. In certainembodiments, nascent oxygen can be produced from decomposition of HOClin solution. Other methods by which nascent oxygen can be producedinclude via electrochemical generation in electrolyte solution, forexample.

In general, nascent oxygen is an efficient oxidizing agent due to therelatively high reactivity of the oxygen radical. However, nascentoxygen can also be a relatively selective oxidizing agent. For example,when lignocellulosic feedstock is treated with nascent oxygen, selectiveoxidation of lignin occurs in preference to the other components of thefeedstock such as cellulose. As a result, oxidation of feedstock withnascent oxygen provides a method for selective removal of the ligninfraction in certain feedstocks. Typically, nascent oxygen concentrationsof between about 0.5% and 5% of the dry weight of the feedstock are usedto effect efficient oxidation.

Without wishing to be bound by theory, it is believed that nascentoxygen reacts with lignocellulosic feedstock according to at least twodifferent mechanisms. In a first mechanism, nascent oxygen undergoes anaddition reaction with the lignin, resulting in partial oxidation of thelignin, which solubilizes the lignin in aqueous solution. As a result,the solubilized lignin can be removed from the rest of the feedstock viawashing. In a second mechanism, nascent oxygen disrupts butanecross-links and/or opens aromatic rings that are connected via thebutane cross-links. As a result, solubility of the lignin in aqueoussolution increases, and the lignin fraction can be separated from theremainder of the feedstock via washing.

In some embodiments, oxidizing agents 5160 include ozone (O₃). The useof ozone can introduce several chemical handling considerations in theoxidation processing sequence. If heated too vigorously, an aqueoussolution of ozone can decompose violently, with potentially adverseconsequences for both human system operators and system equipment.Accordingly, ozone is typically generated in a thermally isolated,thick-walled vessel separate from the vessel that contains the feedstockslurry, and transported thereto at the appropriate process stage.

Without wishing to be bound by theory, it is believed that ozonedecomposes into oxygen and oxygen radicals, and that the oxygen radicals(e.g., nascent oxygen) are responsible for the oxidizing properties ofozone in the manner discussed above. Ozone typically preferentiallyoxidizes the lignin fraction in lignocellulosic materials, leaving thecellulose fraction relatively undisturbed.

Conditions for ozone-based oxidation of biomass feedstock generallydepend upon the nature of the biomass. For example, for cellulosicand/or lignocellulosic feedstocks, ozone concentrations of from 0.1 g/m³to 20 g/m³ of dry feedstock provide for efficient feedstock oxidation.Typically, the water content in slurry 5050 is between 10% by weight and80% by weight (e.g., between 40% by weight and 60% by weight). Duringozone-based oxidation, the temperature of slurry 5050 can be maintainedbetween 0° C. and 100° C. to avoid violent decomposition of the ozone.

In some embodiments, feedstock slurry 5050 can be treated with anaqueous, alkaline solution that includes one or more alkali and alkalineearth hydroxides such as sodium hydroxide, potassium hydroxide, andcalcium hydroxide, and then treated thereafter with an ozone-containinggas in an oxidation reactor. This process has been observed tosignificantly increase decomposition of the biomass in slurry 5050.Typically, for example, a concentration of hydroxide ions in thealkaline solution is between 0.001% and 10% by weight of slurry 5050.After the feedstock has been wetted via contact with the alkalinesolution, the ozone-containing gas is introduced into the oxidationreactor, where it contacts and oxidizes the feedstock.

Oxidizing agents 5160 can also include other substances. In someembodiments, for example, halogen-based oxidizing agents such aschlorine and oxychlorine agents (e.g., hypochlorite) can be introducedinto slurry 5050. In certain embodiments, nitrogen-containing oxidizingsubstances can be introduced into slurry 5050. Exemplarynitrogen-containing oxidizing substances include NO and NO₂, forexample. Nitrogen-containing agents can also be combined with oxygen inslurry 5050 to create additional oxidizing agents. For example, NO andNO₂ both combine with oxygen in slurry 5050 to form nitrate compounds,which are effective oxidizing agents for biomass feedstock. Halogen-andnitrogen-based oxidizing agents can, in some embodiments, causebleaching of the biomass feedstock, depending upon the nature of thefeedstock. The bleaching may be desirable for certain biomass-derivedproducts that are extracted in subsequent processing steps.

Other oxidizing agents can include, for example, various peroxyacids,peroxyacetic acids, persulfates, percarbonates, permanganates, osmiumtetroxide, and chromium oxides.

Following oxidation preprocessing step 5060, feedstock slurry 5050 isoxidized in step 5070. If oxidizing agents 5160 were added to slurry5050 in an oxidation reactor, then oxidation proceeds in the samereactor. Alternatively, if oxidizing agents 5160 were added to slurry5050 in a preprocessing chamber, then slurry 5050 is transported to anoxidation reactor via an in-line piping system. Once inside theoxidation reactor, oxidation of the biomass feedstock proceeds under acontrolled set of environmental conditions. Typically, for example, theoxidation reactor is a cylindrical vessel that is closed to the externalenvironment and pressurized. Both batch and continuous operation ispossible, although environmental conditions are typically easier tocontrol in in-line batch processing operations.

Oxidation of feedstock slurry 5050 typically occurs at elevatedtemperatures in the oxidation reactor. For example, the temperature ofslurry 5050 in the oxidation reactor is typically maintained above 100°C., e.g., in a range from 120° C. to 240° C. For many types of biomassfeedstock, oxidation is particularly efficient if the temperature ofslurry 5050 is maintained between 150° C. and 220° C. Slurry 5050 can beheating using a variety of thermal transfer devices. For example, insome embodiments, the oxidation reactor contacts a heating bath thatincludes oil or molten salts. In certain embodiments, a series of heatexchange pipes surround and contact the oxidation reactor, andcirculation of hot fluid within the pipes heats slurry 5050 in thereactor. Other heating devices that can be used to heat slurry 5050include resistive heating elements, induction heaters, and microwavesources, for example.

The residence time of feedstock slurry 5050 in the oxidation reactor canbe varied as desired to process the feedstock. Typically, slurry 5050spends from 1 minute to 60 minutes undergoing oxidation in the reactor.For relatively soft biomass material such as lignocellulosic matter, theresidence time in the oxidation reactor can be from 5 minutes to 30minutes, for example, at an oxygen pressure of between 3 and 12 bars inthe reactor, and at a slurry temperature of between 160° C. and 210° C.For other types of feedstock, however, residence times in the oxidationreactor can be longer, e.g., as long 48 hours. To determine appropriateresidence times for slurry 5050 in the oxidation reactor, aliquots ofthe slurry can be extracted from the reactor at specific intervals andanalyzed to determine concentrations of particular products of interestsuch as complex saccharides. Information about the increase inconcentrations of certain products in slurry 5050 as a function of timecan be used to determine residence times for particular classes offeedstock material.

In some embodiments, during oxidation of feedstock slurry 5050,adjustment of the slurry pH may be performed by introducing one or morechemical agents into the oxidation reactor. For example, in certainembodiments, oxidation occurs most efficiently in a pH range of about9-11. To maintain a pH in this range, agents such as alkali and alkalineearth hydroxides, carbonates, ammonia, and alkaline buffer solutions canbe introduced into the oxidation reactor.

Circulation of slurry 5050 during oxidation can be important to ensuresufficient contact between oxidizing agents 5160 and the feedstock.Circulation of the slurry can be achieved using a variety of techniques.For example, in some embodiments, a mechanical stirring apparatus thatincludes impeller blades or a paddle wheel can be implemented in theoxidation reactor. In certain embodiments, the oxidation reactor can bea loop reactor, in which the aqueous solvent in which the feedstock issuspended is simultaneously drained from the bottom of the reactor andrecirculated into the top of the reactor via pumping, thereby ensuringthat the slurry is continually re-mixed and does not stagnate within thereactor.

After oxidation of the feedstock is complete, the slurry is transportedto a separation apparatus where a mechanical separation step 5080occurs. Typically, mechanical separation step 5080 includes one or morestages of increasingly-fine filtering of the slurry to mechanicallyseparate the solid and liquid constituents.

Liquid phase 5090 is separated from solid phase 5100, and the two phasesare processed independently thereafter. Solid phase 5100 can optionallyundergo a drying step 5120 in a drying apparatus, for example. Dryingstep 5120 can include, for example, mechanically dispersing the solidmaterial onto a drying surface, and evaporating water from solid phase5100 by gentle heating of the solid material. Following drying step 5120(or, alternatively, without undergoing drying step 5120), solid phase5100 is transported for further processing steps 5140.

Liquid phase 5090 can optionally undergo a drying step 5110 to reducethe concentration of water in the liquid phase. In some embodiments, forexample, drying step 5110 can include evaporation and/or distillationand/or extraction of water from liquid phase 5090 by gentle heating ofthe liquid. Alternatively, or in addition, one or more chemical dryingagents can be used to remove water from liquid phase 5090. Followingdrying step 5110 (or alternatively, without undergoing drying step5110), liquid phase 5090 is transported for further processing steps5130, which can include a variety of chemical and biological treatmentsteps such as chemical and/or enzymatic hydrolysis.

Drying step 5110 creates waste stream 5220, an aqueous solution that caninclude dissolved chemical agents such as acids and bases in relativelylow concentrations. Treatment of waste stream 5220 can include, forexample, pH neutralization with one or more mineral acids or bases.Depending upon the concentration of dissolved salts in waste stream5220, the solution may be partially de-ionized (e.g., by passing thewaste stream through an ion exchange system). Then, the wastestream—which includes primarily water—can be re-circulated into theoverall process (e.g., as water 5150), diverted to another process, ordischarged.

Typically, for lignocellulosic biomass feedstocks following separationstep 5070, liquid phase 5090 includes a variety of soluble poly-andoligosaccharides, which can then be separated and/or reduced tosmaller-chain saccharides via further processing steps. Solid phase 5100typically includes primarily cellulose, for example, with smalleramounts of hemicellulose-and lignin-derived products.

In some embodiments, oxidation can be carried out at elevatedtemperature in a reactor such as a pyrolysis chamber. For example,referring again to FIG. 17, feedstock materials can be oxidized infilament pyrolyzer 1712. In a typical usage, an oxidizing carrier gas,e.g., air or an air/argon blend, traverses through the sample holder1713 while the resistive heating element is rotated and heated to adesired temperature, e.g., 325° C. After an appropriate time, e.g., 5 to10 minutes, the oxidized material is emptied from the sample holder. Thesystem shown in FIG. 17 can be scaled and made continuous. For example,rather than a wire as the heating member, the heating member can be anauger screw. Material can continuously fall into the sample holder,striking a heated screw that pyrolizes the material. At the same time,the screw can push the oxidized material out of the sample holder toallow for the entry of fresh, unoxidized material.

Feedstock materials can also be oxidized in any of the pyrolyzingsystems shown in FIGS. 18-20 and described above.

Referring again to FIG. 21, feedstock materials can be rapidly oxidizedby coating a tungsten filament 150, together with an oxidant, such as aperoxide, with the desired cellulosic material while the material ishoused in a vacuum chamber 151. To affect oxidation, current is passedthrough the filament, which causes a rapid heating of the filament for adesired time. Typically, the heating is continued for seconds beforeallowing the filament to cool. In some embodiments, the heating isperformed a number of times to effect the desired amount of oxidation.

Referring again to FIG. 12, in some embodiments, feedstock materials canbe oxidized with the aid of sound and/or cavitation. Generally, toeffect oxidation, the materials are sonicated in an oxidizingenvironment, such as water saturated with oxygen or another chemicaloxidant, such as hydrogen peroxide.

Referring again to FIGS. 9 and 10, in certain embodiments, ionizingradiation is used to aid in the oxidation of feedstock materials.Generally, to effect oxidation, the materials are irradiated in anoxidizing environment, such as air or oxygen. For example, gammaradiation and/or electron beam radiation can be employed to irradiatethe materials.

Other Processes

Steam explosion can be used alone without any of the processes describedherein, or in combination with any of the processes described herein.

FIG. 23 shows an overview of the entire process of converting a fibersource 400 into a product 450, such as ethanol, by a process thatincludes shearing and steam explosion to produce a fibrous material 401,which is then hydrolyzed and converted, e.g., fermented, to produce theproduct. The fiber source can be transformed into the fibrous material401 through a number of possible methods, including at least oneshearing process and at least one steam explosion process.

For example, one option includes shearing the fiber source, followed byoptional screening step(s) and optional additional shearing step(s) toproduce a sheared fiber source 402, which can then be steam exploded toproduce the fibrous material 401. The steam explosion process isoptionally followed by a fiber recovery process to remove liquids or the“liquor” 404, resulting from the steam exploding process. The materialresulting from steam exploding the sheared fiber source may be furthersheared by optional additional shearing step(s) and/or optionalscreening step(s).

In another method, the fibrous material 401 is first steam exploded toproduce a steam exploded fiber source 410. The resulting steam explodedfiber source is then subjected to an optional fiber recovery process toremove liquids, or the liquor. The resulting steam exploded fiber sourcecan then be sheared to produce the fibrous material. The steam explodedfiber source can also be subject to one or more optional screening stepsand/or one or more optional additional shearing steps. The process ofshearing and steam exploding the fiber source to produce the sheared andsteam exploded fibrous material will be further discussed below.

The fiber source can be cut into pieces or strips of confetti materialprior to shearing or steam explosion. The shearing processes can takeplace with the material in a dry state (e.g., having less than 0.25percent by weight absorbed water), a hydrated state, or even while thematerial is partially or fully submerged in a liquid, such as water orisopropanol. The process can also optimally include steps of drying theoutput after steam exploding or shearing to allow for additional stepsof dry shearing or steam exploding. The steps of shearing, screening,and steam explosion can take place with or without the presence ofvarious chemical solutions.

In a steam explosion process, the fiber source or the sheared fibersource is contacted with steam under high pressure, and the steamdiffuses into the structures of the fiber source (e.g., thelignocellulosic structures). The steam then condenses under highpressure thereby “wetting” the fiber source. The moisture in the fibersource can hydrolyze any acetyl groups in the fiber source (e.g., theacetyl groups in the hemicellulose fractions), forming organic acidssuch as acetic and uronic acids. The acids, in turn, can catalyze thedepolymerization of hemicellulose, releasing xylan and limited amountsof glucan. The “wet” fiber source (or sheared fiber source, etc.) isthen “exploded” when the pressure is released. The condensed moistureinstantaneously evaporates due to the sudden decrease in pressure andthe expansion of the water vapor exerts a shear force upon the fibersource (or sheared fiber source, etc.). A sufficient shear force willcause the mechanical breakdown of the internal structures (e.g., thelignocellulosic structures) of the fiber source.

The sheared and steam exploded fibrous material is then converted into auseful product, such as ethanol. In some embodiments, the fibrousmaterial is converted into a fuel. One method of converting the fibrousmaterial into a fuel is by hydrolysis to produce fermentable sugars,412, which are then fermented to produce the product. Other methods ofconverting fibrous materials into fuels may also be used.

In some embodiments, prior to combining with the microorganism, thesheared and steam exploded fibrous material 401 is sterilized to killany competing microorganisms that may be on the fibrous material. Forexample, the fibrous material can be sterilized by exposing the fibrousmaterial to radiation, such as infrared radiation, ultravioletradiation, or an ionizing radiation, such as gamma radiation. Themicroorganisms can also be killed using chemical sterilants, such asbleach (e.g., sodium hypochlorite), chlorhexidine, or ethylene oxide.

One method to hydrolyze the sheared and steam exploded fibrous materialis by the use of cellulases. Cellulases are a group of enzymes that actsynergistically to hydrolyze cellulose. Commercially availableAccellerase® 1000 enzyme complex, which contains a complex of enzymesthat reduces lignocellulosic biomass into fermentable sugars can also beused.

According to current understanding, the components of cellulase includeendoglucanases, exoglucanases (cellobiohydrolases), and β-glucosidases(cellobiases). Synergism between the cellulase components exists whenhydrolysis by a combination of two or more components exceeds the sum ofthe activities expressed by the individual components. The generallyaccepted mechanism of action of a cellulase system (particularly of T.longibrachiatum) on crystalline cellulose is: endoglucanase hydrolyzesinternal β-1,4-glycosidic bonds of the amorphous regions, therebyincreasing the number of exposed non-reducing ends. Exoglucanases thencleave off cellobiose units from the nonreducing ends, which in turn arehydrolyzed to individual glucose units by β-glucosidases. There areseveral configurations of both endo-and exo-glucanases differing instereospecificities. In general, the synergistic action of thecomponents in various configurations is required for optimum cellulosehydrolysis. Cellulases, however, are more inclined to hydrolyze theamorphous regions of cellulose. A linear relationship betweencrystallinity and hydrolysis rates exists whereby higher crystallinityindices correspond to slower enzyme hydrolysis rates. Amorphous regionsof cellulose hydrolyze at twice the rate of crystalline regions. Thehydrolysis of the sheared and steam exploded fibrous material may beperformed by any hydrolyzing biomass process.

Steam explosion of biomass sometimes causes the formation ofby-products, e.g., toxicants, that are inhibitory to microbial andenzymatic activities. The process of converting the sheared and steamexploded fibrous material into a fuel can therefore optionally includean overliming step prior to fermentation to precipitate some of thetoxicants. For example, the pH of the sheared and steam exploded fibrousmaterial may be raised to exceed the pH of 10 by adding calciumhydroxide (Ca(OH)₂) followed by a step of lowering the pH to about 5 byadding H₂SO₄. The overlimed fibrous material may then be used as iswithout the removal of precipitates. As shown in FIG. 23, the optionaloverliming step occurs just prior to the step of hydrolysis of thesheared and steam exploded fibrous material, but it is also contemplatedto perform the overliming step after the hydrolysis step and prior tothe fermenting step.

FIG. 24 depicts an example of a steam explosion apparatus 460. The steamexplosion apparatus 460 includes a reaction chamber 462, in which thefiber source and/or the fibrous material is placed through a fibersource inlet 464. The reaction chamber is sealed by closing fiber sourceinlet valve 465. The reaction chamber includes a pressurized steam inlet466 that includes a steam valve 467. The reaction chamber furtherincludes an explosive depressurization outlet 468 that includes anoutlet valve 469 in communication with the cyclone 470 through theconnecting pipe 472. Once the reaction chamber contains the fiber sourceand/or sheared fiber source and is sealed by closing valves 465, 467 and469, steam is delivered into the reaction chamber 462 by opening thesteam inlet valve 467 allowing steam to travel through steam inlet 466.Once the reaction chamber reaches target temperature, which can takeabout 20-60 seconds, the holding time begins. The reaction chamber isheld at the target temperature for the desired holding time, whichtypically lasts from about 10 seconds to 5 minutes. At the end of theholding time period, outlet valve is opened to allow for explosivedepressurization to occur. The process of explosive depressurizationpropels the contents of the reaction chamber 462 out of the explosivedepressurization outlet 468, through the connecting pipe 472, and intothe cyclone 470. The steam exploded fiber source or fibrous materialthen exits the cyclone in a sludge form into the collection bin 474 asmuch of the remaining steam exits the cyclone into the atmospherethrough vent 476. The steam explosion apparatus further includes washoutlet 478 with wash outlet valve 479 in communication with connectingpipe 472. The wash outlet valve 479 is closed during the use of thesteam explosion apparatus 460 for steam explosion, but opened during thewashing of the reaction chamber 462.

The target temperature of the reaction chamber 462 is preferably between180 and 240 degrees Celsius or between 200 and 220 degrees Celsius. Theholding time is preferably between 10 seconds and 30 minutes, or between30 seconds and 10 minutes, or between 1 minute and 5 minutes.

Because the steam explosion process results in a sludge of steamexploded fibrous material, the steam exploded fibrous material mayoptionally include a fiber recovery process where the “liquor” isseparated from the steam exploded fibrous material. This fiber recoverystep is helpful in that it enables further shearing and/or screeningprocesses and can allow for the conversion of the fibrous material intofuel. The fiber recovery process occurs through the use of a mesh clothto separate the fibers from the liquor. Further drying processes canalso be included to prepare the fibrous material or steam exploded fibersource for subsequent processing.

Combined Irradiating, Sonicating, Pyrolyzing and/or Oxidizing Devices

In some embodiments, it may be advantageous to combine two or moreseparate irradiation, sonication, pyrolization, and/or oxidation devicesinto a single hybrid machine. Using such a hybrid machine, multipleprocesses may be performed in close juxtaposition or evensimultaneously, with the benefit of increasing pretreatment throughputand potential cost savings.

For example, consider the electron beam irradiation and sonicationprocesses. Each separate process is effective in lowering the meanmolecular weight of cellulosic material by an order of magnitude ormore, and by several orders of magnitude when performed serially.

Both irradiation and sonication processes can be applied using a hybridelectron beam/sonication device as is illustrated in FIG. 25. Hybridelectron beam/sonication device 2500 is pictured above a shallow pool(depth ˜3-5 cm) of a slurry of cellulosic material 2550 dispersed in anaqueous, oxidant medium, such as hydrogen peroxide or carbamideperoxide. Hybrid device 2500 has an energy source 2510, which powersboth electron beam emitter 2540 and sonication horns 2530.

Electron beam emitter 2540 generates electron beams which pass though anelectron beam aiming device 2545 to impact the slurry 2550 containingcellulosic material. The electron beam aiming device can be a scannerthat sweeps a beam over a range of up to about 6 feet in a directionapproximately parallel to the surface of the slurry 2550.

On either side of the electron beam emitter 2540 are sonication horns2530, which deliver ultrasonic wave energy to the slurry 2550. Thesonication horns 2530 end in a detachable endpiece 2535 that is incontact with the slurry 2550.

The sonication horns 2530 are at risk of damage from long-term residualexposure to the electron beam radiation. Thus, the horns can beprotected with a standard shield 2520, e.g., made of lead or aheavy-metal-containing alloy such as Lipowitz metal, which is imperviousto electron beam radiation. Precautions must be taken, however, toensure that the ultrasonic energy is not affected by the presence of theshield. The detachable endpieces 2535, which are constructed of the samematerial and attached to the horns 2530, are in contact with thecellulosic material 2550 during processing and are expected to bedamaged. Accordingly, the detachable endpieces 2535 are constructed tobe easily replaceable.

A further benefit of such a simultaneous electron beam and ultrasoundprocess is that the two processes have complementary results. Withelectron beam irradiation alone, an insufficient dose may result incross-linking of some of the polymers in the cellulosic material, whichlowers the efficiency of the overall depolymerization process. Lowerdoses of electron beam irradiation and/or ultrasound radiation may alsobe used to achieve a similar degree of depolymerization as that achievedusing electron beam irradiation and sonication separately. An electronbeam device can also be combined with one or more of high-frequency,rotor-stator devices, which can be used as an alternative to ultrasonicenergy devices.

Further combinations of devices are also possible. For example, anionizing radiation device that produces gamma radiation emitted from,e.g., ⁶⁰Co pellets, can be combined with an electron beam source and/oran ultrasonic wave source. Shielding requirements may be more stringentin this case.

The radiation devices for pretreating biomass discussed above can alsobe combined with one or more devices that perform one or more pyrolysisprocessing sequences. Such a combination may again have the advantage ofhigher throughput. Nevertheless, caution must be observed, as there maybe conflicting requirements between some radiation processes andpyrolysis. For example, ultrasonic radiation devices may require thefeedstock be immersed in a liquid oxidizing medium. On the other hand,as discussed previously, it may be advantageous for a sample offeedstock undergoing pyrolysis to be of a particular moisture content.In this case, the new systems automatically measure and monitor for aparticular moisture content and regulate the same. Further, some or allof the above devices, especially the pyrolysis device, can be combinedwith an oxidation device as discussed previously.

Primary Processes

Fermentation

Generally, various microorganisms can produce a number of usefulproducts, such as a fuel, by operating on, e.g., fermenting thepretreated biomass materials. For example, alcohols, organic acids,hydrocarbons, hydrogen, proteins or mixtures of any of these materialscan be produced by fermentation or other processes.

The microorganism can be a natural microorganism or an engineeredmicroorganism. For example, the microorganism can be a bacterium, e.g.,a cellulolytic bacterium, a fungus, e.g., a yeast, a plant or a protist,e.g., an algae, a protozoa or a fungus-like protist, e.g., a slime mold.When the organisms are compatible, mixtures of organisms can beutilized.

To aid in the breakdown of the materials that include the cellulose, oneor more enzymes, e.g., a cellulolytic enzyme can be utilized. In someembodiments, the materials that include the cellulose are first treatedwith the enzyme, e.g., by combining the material and the enzyme in anaqueous solution. This material can then be combined with themicroorganism. In other embodiments, the materials that include thecellulose, the one or more enzymes and the microorganism are combined atthe concurrently, e.g., by combining in an aqueous solution.

Also, to aid in the breakdown of the materials that include thecellulose, the materials can be treated post irradiation with heat, achemical (e.g., mineral acid, base or a strong oxidizer such as sodiumhypochlorite), and/or an enzyme.

During the fermentation, sugars released from cellulolytic hydrolysis orthe saccharification step, are fermented to, e.g., ethanol, by afermenting microorganism such as yeast. Suitable fermentingmicroorganisms have the ability to convert carbohydrates, such asglucose, xylose, arabinose, mannose, galactose, oligosaccharides orpolysaccharides into fermentation products. Fermenting microorganismsinclude strains of the genus Sacchromyces spp. e.g., Sacchromycescerevisiae (baker's yeast), Saccharomyces distaticus, Saccharomycesuvarum; the genus Kluyveromyces, e.g., species Kluyveromyces marxianus,Kluyveromyces fragilis; the genus Candida, e.g., Candidapseudotropicalis, and Candida brassicae, the genus Clavispora, e.g.,species Clavispora lusitaniae and Clavispora opuntiae the genusPachysolen, e.g., species Pachysolen tannophilus, the genusBretannomyces, e.g., species Bretannomyces clausenii (Philippidis, G.P., 1996, Cellulose bioconversion technology, in Handbook on Bioethanol:Production and Utilization, Wyman, C. E., ed., Taylor & Francis,Washington, D.C., 179-212).

Commercially available yeast include, for example, Red Star®/LesaffreEthanol Red (available from Red Star/Lesaffre, USA) FALI® (availablefrom Fleischmann's Yeast, a division of Burns Philip Food Inc., USA),SUPERSTART® (available from Lallemand, formerly Alltech), GERT STRAND®(available from Gert Strand AB, Sweden) and FERMOL® (available from DSMSpecialties).

Bacteria that can ferment biomass to ethanol and other products include,e.g., Zymomonas mobilis and Clostridium thermocellum (Philippidis, 1996,supra). Leschine et al. (International Journal of Systematic andEvolutionary Microbiology 2002, 52, 1155-1160) isolated an anaerobic,mesophilic, cellulolytic bacterium from forest soil, Clostridiumphytofermentans sp. nov., which converts cellulose to ethanol.

Fermentation of biomass to ethanol and other products may be carried outusing certain types of thermophilic or genetically engineeredmicroorganisms, such Thermoanaerobacter species, including T. mathranii,and yeast species such as Pichia species. An example of a strain of T.mathranii is A3M4 described in Sonne-Hansen et al. (Applied Microbiologyand Biotechnology 1993, 38, 537-541) or Ahring et al. (Arch. Microbiol.1997, 168, 114-119).

Yeast and Zymomonas bacteria can be used for fermentation or conversion.The optimum pH for yeast is from about pH 4 to 5, while the optimum pHfor Zymomonas is from about pH 5 to 6. Typical fermentation times areabout 24 to 96 hours with temperatures in the range of 26° C. to 40° C.,however thermophilic microorganisms prefer higher temperatures.

Enzymes which break down biomass, such as cellulose, to lower molecularweight carbohydrate-containing materials, such as glucose, duringsaccharification are referred to as cellulolytic enzymes or cellulase.These enzymes may be a complex of enzymes that act synergistically todegrade crystalline cellulose. Examples of cellulolytic enzymes include:endoglucanases, cellobiohydrolases, and cellobiases (β-glucosidases). Acellulosic substrate is initially hydrolyzed by endoglucanases at randomlocations producing oligomeric intermediates. These intermediates arethen substrates for exo-splitting glucanases such as cellobiohydrolaseto produce cellobiose from the ends of the cellulose polymer. Cellobioseis a water-soluble β-1,4-linked dimer of glucose. Finally cellobiasecleaves cellobiose to yield glucose.

A cellulase is capable of degrading biomass and may be of fungal orbacterial origin. Suitable enzymes include cellulases from the generaBacillus, Pseudomonas, Humicola, Fusarium, Thielavia, Acremonium,Chrysosporium and Trichoderma, and include species of Humicola,Coprinus, Thielavia, Fusarium, Myceliophthora, Acremonium,Cephalosporium, Scytalidium, Penicillium or Aspergillus (see, e.g., EP458162), especially those produced by a strain selected from the speciesHumicola insolens (reclassified as Scytalidium thermophilum, see, e.g.,U.S. Pat. No. 4,435,307), Coprinus cinereus, Fusarium oxysporum,Myceliophthora thermophile, Meripilus giganteus, Thielavia terrestris,Acremonium sp., Acremonium persicinum, Acremonium acremonium, Acremoniumbrachypenium, Acremonium dichromosporum, Acremonium obclavatum,Acremonium pinkertoniae, Acremonium roseogriseum, Acremoniumincoloratum, and Acremonium furatum; preferably from the speciesHumicola insolens DSM 1800, Fusarium oxysporum DSM 2672, Myceliophthorathermophile CBS 117.65, Cephalosporium sp. RYM-202, Acremonium sp. CBS478.94, Acremonium sp. CBS 265.95, Acremonium persicinum CBS 169.65,Acremonium acremonium AHU 9519, Cephalosporium sp. CBS 535.71,Acremonium brachypenium CBS 866.73, Acremonium dichromosporum CBS683.73, Acremonium obclavatum CBS 311.74, Acremonium pinkertoniaeCBS157.70, Acremonium roseogriseum CBS134.56, Acremonium incoloratumCBS146.62, and Acremonium furatum CBS 299.70H. Cellulolytic enzymes mayalso be obtained from Chrysosporium, preferably a strain ofChrysosporium lucknowense. Additionally, Trichoderma (particularlyTrichoderma viride, Trichoderma reesei, and Trichoderma koningii),alkalophilic Bacillus (see, for example, U.S. Pat. No. 3,844,890 and EP458162), and Streptomyces (see, e.g., EP 458162) may be used.

Anaerobic cellulolytic bacteria have also been isolated from soil, e.g.,a novel cellulolytic species of Clostiridium, Clostridiumphytofermentans sp. nov. (see Leschine et. al, International Journal ofSystematic and Evolutionary Microbiology (2002), 52, 1155-1160).

Cellulolytic enzymes using recombinant technology can also be used (see,e.g., WO 2007/071818 and WO 2006/110891).

The cellulolytic enzymes used can be produced by fermentation of theabove-noted microbial strains on a nutrient medium containing suitablecarbon and nitrogen sources and inorganic salts, using procedures knownin the art (see, e.g., Bennett, J. W. and LaSure, L. (eds.), More GeneManipulations in Fungi, Academic Press, CA 1991). Suitable media areavailable from commercial suppliers or may be prepared according topublished compositions (e.g., in catalogues of the American Type CultureCollection). Temperature ranges and other conditions suitable for growthand cellulase production are known in the art (see, e.g., Bailey, J. E.,and Ollis, D. F., Biochemical Engineering Fundamentals, McGraw-Hill BookCompany, NY, 1986).

Treatment of cellulose with cellulase is usually carried out attemperatures between 30° C. and 65° C. Cellulases are active over arange of pH of about 3 to 7. A saccharification step may last up to 120hours. The cellulase enzyme dosage achieves a sufficiently high level ofcellulose conversion. For example, an appropriate cellulase dosage istypically between 5.0 and 50 Filter Paper Units (FPU or IU) per gram ofcellulose. The FPU is a standard measurement and is defined and measuredaccording to Ghose (1987, Pure and Appl. Chem. 59:257-268).

Gasification

In addition to using pyrolysis for pre-treatment of feedstock, pyrolysiscan also be used to process pre-treated feedstock to extract usefulmaterials. In particular, a form of pyrolysis known as gasification canbe employed to generate fuel gases along with various other gaseous,liquid, and solid products. To perform gasification, the pre-treatedfeedstock is introduced into a pyrolysis chamber and heated to a hightemperature, typically 700° C. or more. The temperature used dependsupon a number of factors, including the nature of the feedstock and thedesired products.

Quantities of oxygen (e.g., as pure oxygen gas and/or as air) and steam(e.g., superheated steam) are also added to the pyrolysis chamber tofacilitate gasification. These compounds react with carbon-containingfeedstock material in a multiple-step reaction to generate a gas mixturecalled synthesis gas (or “syngas”). Essentially, during gasification, alimited amount of oxygen is introduced into the pyrolysis chamber toallow some feedstock material to combust to form carbon monoxide andgenerate process heat. The process heat can then be used to promote asecond reaction that converts additional feedstock material to hydrogenand carbon monoxide.

In a first step of the overall reaction, heating the feedstock materialproduces a char that can include a wide variety of differenthydrocarbon-based species. Certain volatile materials can be produced(e.g., certain gaseous hydrocarbon materials), resulting in a reductionof the overall weight of the feedstock material. Then, in a second stepof the reaction, some of the volatile material that is produced in thefirst step reacts with oxygen in a combustion reaction to produce bothcarbon monoxide and carbon dioxide. The combustion reaction releasesheat, which promotes the third step of the reaction. In the third step,carbon dioxide and steam (e.g., water) react with the char generated inthe first step to form carbon monoxide and hydrogen gas. Carbon monoxidecan also react with steam, in a water gas shift reaction, to form carbondioxide and further hydrogen gas.

Gasification can be used as a primary process to generate productsdirectly from pre-treated feedstock for subsequent transport and/orsale, for example. Alternatively, or in addition, gasification can beused as an auxiliary process for generating fuel for an overallprocessing system. The hydrogen-rich syngas that is generated via thegasification process can be burned, for example, to generate electricityand/or process heat that can be directed for use at other locations inthe processing system. As a result, the overall processing system can beat least partially self-sustaining. A number of other products,including pyrolysis oils and gaseous hydrocarbon-based substances, canalso be obtained during and/or following gasification; these can beseparated and stored or transported as desired.

A variety of different pyrolysis chambers are suitable for gasificationof pre-treated feedstock, including the pyrolysis chambers disclosedherein. In particular, fluidized bed reactor systems, in which thepre-treated feedstock is fluidized in steam and oxygen/air, providerelatively high throughput and straightforward recovery of products.Solid char that remains following gasification in a fluidized bed system(or in other pyrolysis chambers) can be burned to generate additionalprocess heat to promote subsequent gasification reactions.

Post-Processing

Distillation

After fermentation, the resulting fluids can be distilled using, forexample, a “beer column” to separate ethanol and other alcohols from themajority of water and residual solids. The vapor exiting the beer columncan be, for example, 35% by weight ethanol and can be fed to arectification column. A mixture of nearly azeotropic (92.5%) ethanol andwater from the rectification column can be purified to pure (99.5%)ethanol using vapor-phase molecular sieves. The beer column bottoms canbe sent to the first effect of a three-effect evaporator. Therectification column reflux condenser can provide heat for this firsteffect. After the first effect, solids can be separated using acentrifuge and dried in a rotary dryer. A portion (25%) of thecentrifuge effluent can be recycled to fermentation and the rest sent tothe second and third evaporator effects. Most of the evaporatorcondensate can be returned to the process as fairly clean condensatewith a small portion split off to waste water treatment to preventbuild-up of low-boiling compounds.

Waste Water Treatment

Wastewater treatment is used to minimize makeup water requirements ofthe plant by treating process water for reuse within the plant.Wastewater treatment can also produce fuel (e.g., sludge and biogas)that can be used to improve the overall efficiency of the ethanolproduction process. For example, as described in further detail below,sludge and biogas can be used to create steam and electricity that canbe used in various plant processes.

Wastewater is initially pumped through a screen (e.g., a bar screen) toremove large particles, which are collected in a hopper. In someembodiments, the large particles are sent to a landfill. Additionally oralternatively, the large particles are burned to create steam and/orelectricity as described in further detail below. In general, thespacing on the bar screen is between ¼ inch to 1 inch spacing (e.g., ½inch spacing).

The wastewater then flows to an equalization tank, where the organicconcentration of the wastewater is equalized during a retention time. Ingeneral, the retention time is between 8 hours and 36 hours (e.g., 24hours). A mixer is disposed within the tank to stir the contents of thetank. In some embodiments, a plurality of mixers disposed throughout thetank are used to stir the contents of the tank. In certain embodiments,the mixer substantially mixes the contents of the equalization tank suchthat conditions (e.g., wastewater concentration and temperature)throughout the tank are uniform.

A first pump moves water from the equalization tank through aliquid-to-liquid heat exchanger. The heat exchanger is controlled (e.g.,by controlling the flow rate of fluid through the heat exchanger) suchthat wastewater exiting the heat exchanger is at a desired temperaturefor anaerobic treatment. For example, the desired temperature foranaerobic treatment can be between 40° C. to 60° C.

After exiting the heat exchanger, the wastewater enters one or moreanaerobic reactors. In some embodiments, the concentration of sludge ineach anaerobic reactor is the same as the overall concentration ofsludge in the wastewater. In other embodiments, the anaerobic reactorhas a higher concentration of sludge than the overall concentration ofsludge in the wastewater.

A nutrient solution containing nitrogen and phosphorus is metered intoeach anaerobic reactor containing wastewater. The nutrient solutionreacts with the sludge in the anaerobic reactor to produce biogas whichcan contain 50% methane and have a heating value of approximately 12,000British thermal units, or Btu, per pound). The biogas exits eachanaerobic reactor through a vent and flows into a manifold, where aplurality of biogas streams are combined into a single stream. Acompressor moves the stream of biogas to a boiler or a combustion engineas described in further detail below. In some embodiments, thecompressor also moves the single stream of biogas through adesulphurization catalyst. Additionally or alternatively, the compressorcan move the single stream of biogas through a sediment trap.

A second pump moves anaerobic effluent from the anaerobic reactors toone or more aerobic reactors (e.g., activated sludge reactors). Anaerator is disposed within each aerobic reactor to mix the anaerobiceffluent, sludge, and oxygen (e.g., oxygen contained in air). Withineach aerobic reactor, oxidation of cellular material in the anaerobiceffluent produces carbon dioxide, water, and ammonia.

Aerobic effluent moves (e.g., via gravity) to a separator, where sludgeis separated from treated water. Some of the sludge is returned to theone or more aerobic reactors to create an elevated sludge concentrationin the aerobic reactors, thereby facilitating the aerobic breakdown ofcellular material in the wastewater. A conveyor removes excess sludgefrom the separator. As described in further detail below, the excesssludge is used as fuel to create steam and/or electricity.

The treated water is pumped from the separator to a settling tank.Solids dispersed throughout the treated water settle to the bottom ofthe settling tank and are subsequently removed. After a settling period,treated water is pumped from the settling tank through a fine filter toremove any additional solids remaining in the water. In someembodiments, chlorine is added to the treated water to kill pathogenicbacteria. In some embodiments, one or more physical-chemical separationtechniques are used to further purify the treated water. For example,treated water can be pumped through a carbon adsorption reactor. Asanother example, treated water can pumped through a reverse osmosisreactor.

Waste Combustion

The production of alcohol from biomass can result in the production ofvarious by-product streams useful for generating steam and electricityto be used in other parts of the plant. For example, steam generatedfrom burning by-product streams can be used in the distillation process.As another example, electricity generated from burning by-productstreams can be used to power electron beam generators and ultrasonictransducers used in pretreatment.

The by-products used to generate steam and electricity are derived froma number of sources throughout the process. For example, anaerobicdigestion of wastewater produces a biogas high in methane and a smallamount of waste biomass (sludge). As another example, post-distillatesolids (e.g., unconverted lignin, cellulose, and hemicellulose remainingfrom the pretreatment and primary processes) can be used as a fuel.

The biogas is diverted to a combustion engine connected to an electricgenerator to produce electricity. For example, the biogas can be used asa fuel source for a spark-ignited natural gas engine. As anotherexample, the biogas can be used as a fuel source for a direct-injectionnatural gas engine. As another example, the biogas can be used as a fuelsource for a combustion turbine. Additionally or alternatively, thecombustion engine can be configured in a cogeneration configuration. Forexample, waste heat from the combustion engines can be used to providehot water or steam throughout the plant.

The sludge, and post-distillate solids are burned to heat water flowingthrough a heat exchanger. In some embodiments, the water flowing throughthe heat exchanger is evaporated and superheated to steam. In certainembodiments, the steam is used in the pretreatment rector and in heatexchange in the distillation and evaporation processes. Additionally oralternatively, the steam expands to power a multi-stage steam turbineconnected to an electric generator. Steam exiting the steam turbine iscondensed with cooling water and returned to the heat exchanger forreheating to steam. In some embodiments, the flow rate of water throughthe heat exchanger is controlled to obtain a target electricity outputfrom the steam turbine connected to an electric generator. For example,water can be added to the heat exchanger to ensure that the steamturbine is operating above a threshold condition (e.g., the turbine isspinning fast enough to turn the electric generator).

While certain embodiments have been described, other embodiments arepossible.

As an example, while the biogas is described as being diverted to acombustion engine connected to an electric generator, in certainembodiments, the biogas can be passed through a fuel reformer to producehydrogen. The hydrogen is then converted to electricity through a fuelcell.

As another example, while the biogas is described as being burned apartfrom the sludge and post-distillate solids, in certain embodiments, allof the waste by-products can be burned together to produce steam.

Products/Co-Products

Alcohols

The alcohol produced can be a monohydroxy alcohol, e.g., ethanol, or apolyhydroxy alcohol, e.g., ethylene glycol or glycerin. Examples ofalcohols that can be produced include methanol, ethanol, propanol,isopropanol, butanol, e.g., n-, sec-or t-butanol, ethylene glycol,propylene glycol, 1,4-butane diol, glycerin or mixtures of thesealcohols.

Each of the alcohols produced by the plant have commercial value asindustrial feedstock. For example, ethanol can be used in themanufacture of varnishes and perfume. As another example, methanol canbe used as a solvent used as a component in windshield wiper fluid. Asstill another example, butanol can be used in plasticizers, resins,lacquers, and brake fluids.

Bioethanol produced by the plant is valuable as an ingredient used inthe food and beverage industry. For example, the ethanol produced by theplant can be purified to food grade alcohol and used as a primaryingredient in the alcoholic beverages.

Bioethanol produced by the plant also has commercial value as atransportation fuel. The use of ethanol as a transportation fuel can beimplemented with relatively little capital investment from sparkignition engine manufacturers and owners (e.g., changes to injectiontiming, fuel-to-air ratio, and components of the fuel injection system).Many automotive manufacturers currently offer flex-fuel vehicles capableof operation on ethanol/gasoline blends up to 85% ethanol by volume(e.g., standard equipment on a Chevy Tahoe 4×4).

Bioethanol produced by this plant can be used as an engine fuel toimprove environmental and economic conditions beyond the location of theplant. For example, ethanol produced by this plant and used as a fuelcan reduce greenhouse gas emissions from manmade sources (e.g.,transportation sources). As another example, ethanol produced by thisplant and used as an engine fuel can also displace consumption ofgasoline refined from oil.

Bioethanol has a greater octane number than conventional gasoline and,thus, can be used to improve the performance (e.g., allow for highercompression ratios) of spark ignition engines. For example, smallamounts (e.g., 10% by volume) of ethanol can be blended with gasoline toact as an octane enhancer for fuels used in spark ignition engines. Asanother example, larger amounts (e.g., 85% by volume) of ethanol can beblended with gasoline to further increase the fuel octane number anddisplace larger volumes of gasoline.

Bioethanol strategies are discussed, e.g., by DiPardo in Journal ofOutlook for Biomass Ethanol Production and Demand (EIA Forecasts), 2002;Sheehan in Biotechnology Progress, 15:8179, 1999; Martin in EnzymeMicrobes Technology, 31:274, 2002; Greer in BioCycle, 61-65, April 2005;Lynd in Microbiology and Molecular Biology Reviews, 66:3, 506-577, 2002;Ljungdahl et al. in U.S. Pat. No. 4,292,406; and Bellamy in U.S. Pat.No. 4,094,742.

Organic Acids

The organic acids produced can include monocarboxylic acids or apolycarboxylic acids. Examples of organic acids include formic acid,acetic acid, propionic acid, butyric acid, valeric acid, caproic,palmitic acid, stearic acid, oxalic acid, malonic acid, succinic acid,glutaric acid, oleic acid, linoleic acid, glycolic acid, lactic acid,γ-hydroxybutyric acid or mixtures of these acids.

Food Products

In some embodiments, all or a portion of the fermentation process can beinterrupted before the cellulosic material is completely converted toethanol. The intermediate fermentation products include highconcentrations of sugar and carbohydrates. These intermediatefermentation products can be used in preparation of food for human oranimal consumption. In some embodiments, irradiation pretreatment of thecellulosic material will render the intermediate fermentation productssterile (e.g., fit for human consumption). In some embodiments, theintermediate fermentation products will require post-processing prior touse as food. For example, a dryer can be used to remove moisture fromthe intermediate fermentation products to facilitate storage, handling,and shelf-life. Additionally or alternatively, the intermediatefermentation products can be ground to a fine particle size in astainless-steel laboratory mill to produce a flour-like substance.

Animal Feed

Distillers grains and solubles can be converted into a valuablebyproduct of the distillation-dehydration process. After thedistillation-dehydration process, distillers grains and solubles can bedried to improve the ability to store and handle the material. Theresulting dried distillers grains and solubles (DDGS) is low in starch,high in fat, high in protein, high in fiber, and high in phosphorous.Thus, for example, DDGS can be valuable as a source of animal feed(e.g., as a feed source for dairy cattle). DDGS can be subsequentlycombined with nutritional additives to meet specific dietaryrequirements of specific categories of animals (e.g., balancingdigestible lysine and phosphorus for swine diets).

Pharmaceuticals

The pretreatment processes discussed above can be applied to plants withmedicinal properties. In some embodiments, sonication can stimulatebioactivity and/or bioavailability of the medicinal components of plantswith medicinal properties. Additionally or alternatively, irradiationstimulates bioactivity and/or bioavailability of the medicinalcomponents of plants with medicinal properties. For example, sonicationand irradiation can be combined in the pretreatment of willow bark tostimulate the production of salicin.

Nutriceuticals

In some embodiments, intermediate fermentation products (e.g., productsthat include high concentrations of sugar and carbohydrates) can besupplemented to create a nutriceutical. For example, intermediatefermentation products can be supplemented with calcium create anutriceutical that provides energy and helps improve or maintain bonestrength.

Co-Products

Lignin Residue

As described above, lignin containing residues from primary andpretreatment processes has value as a high/medium energy fuel and can beused to generate power and steam for use in plant processes. However,such lignin residues are a new type of solids fuel and there is littledemand for it outside of the plant boundaries, and the costs of dryingit for transportation only subtract from its potential value. In somecases, gasification of the lignin residues can converting it to ahigher-value product with lower cost.

Other Co-Products

Cell matter, furfural, and acetic acid have been identified as potentialco-products of biomass-to-fuel processing facilities. Interstitial cellmatter could be valuable, but might require significant purification.Markets for furfural and acetic acid are in place, although it isunlikely that they are large enough to consume the output of a fullycommercialized lignocellulose-to-ethanol industry.

EXAMPLES

The following Examples are intended to illustrate, and do not limit theteachings of this disclosure.

Example 1 Preparation of Fibrous Material from Polycoated Paper

A 1500 pound skid of virgin, half-gallon juice cartons made ofun-printed polycoated white Kraft board having a bulk density of 20lb/ft³ was obtained from International Paper. Each carton was foldedflat, and then fed into a 3 hp Flinch Baugh shredder at a rate ofapproximately 15 to 20 pounds per hour. The shredder was equipped withtwo 12 inch rotary blades, two fixed blades and a 0.30 inch dischargescreen. The gap between the rotary and fixed blades was adjusted to 0.10inch. The output from the shredder resembled confetti having a width ofbetween 0.1 inch and 0.5 inch, a length of between 0.25 inch and 1 inchand a thickness equivalent to that of the starting material (about 0.075inch).

The confetti-like material was fed to a Munson rotary knife cutter,Model SC30. Model SC30 is equipped with four rotary blades, four fixedblades, and a discharge screen having ⅛ inch openings. The gap betweenthe rotary and fixed blades was set to approximately 0.020 inch. Therotary knife cutter sheared the confetti-like pieces across theknife-edges, tearing the pieces apart and releasing a fibrous materialat a rate of about one pound per hour. The fibrous material had a BETsurface area of 0.9748 m²/g+/−0.0167 m²/g, a porosity of 89.0437 percentand a bulk density (@0.53 psia) of 0.1260 g/mL. An average length of thefibers was 1.141 mm and an average width of the fibers was 0.027 mm,giving an average L/D of 42:1. A scanning electron micrograph of thefibrous material is shown in FIG. 26 at 25× magnification.

Example 2 Preparation of Fibrous Material from Bleached Kraft Board

A 1500 pound skid of virgin bleached white Kraft board having a bulkdensity of 30 lb/ft³ was obtained from International Paper. The materialwas folded flat, and then fed into a 3 hp Flinch Baugh shredder at arate of approximately 15 to 20 pounds per hour. The shredder wasequipped with two 12 inch rotary blades, two fixed blades and a 0.30inch discharge screen. The gap between the rotary and fixed blades wasadjusted to 0.10 inch. The output from the shredder resembled confettihaving a width of between 0.1 inch and 0.5 inch, a length of between0.25 inch and 1 inch and a thickness equivalent to that of the startingmaterial (about 0.075 inch). The confetti-like material was fed to aMunson rotary knife cutter, Model SC30. The discharge screen had ⅛ inchopenings. The gap between the rotary and fixed blades was set toapproximately 0.020 inch. The rotary knife cutter sheared theconfetti-like pieces, releasing a fibrous material at a rate of aboutone pound per hour. The fibrous material had a BET surface area of1.1316 m²/g+/−0.0103 m²/g, a porosity of 88.3285 percent and a bulkdensity (@0.53 psia) of 0.1497 g/mL. An average length of the fibers was1.063 mm and an average width of the fibers was 0.0245 mm, giving anaverage L/D of 43:1. A scanning electron micrographs of the fibrousmaterial is shown in FIG. 27 at 25× magnification.

Example 3 Preparation of Twice Sheared Fibrous Material from BleachedKraft Board

A 1500 pound skid of virgin bleached white Kraft board having a bulkdensity of 30 lb/ft³ was obtained from International Paper. The materialwas folded flat, and then fed into a 3 hp Flinch Baugh shredder at arate of approximately 15 to 20 pounds per hour. The shredder wasequipped with two 12 inch rotary blades, two fixed blades and a 0.30inch discharge screen. The gap between the rotary and fixed blades wasadjusted to 0.10 inch. The output from the shredder resembled confetti(as above). The confetti-like material was fed to a Munson rotary knifecutter, Model SC30. The discharge screen had 1/16 inch openings. The gapbetween the rotary and fixed blades was set to approximately 0.020 inch.The rotary knife cutter the confetti-like pieces, releasing a fibrousmaterial at a rate of about one pound per hour. The material resultingfrom the first shearing was fed back into the same setup described aboveand sheared again. The resulting fibrous material had a BET surface areaof 1.4408 m²/g+/−0.0156 m²/g, a porosity of 90.8998 percent and a bulkdensity (@0.53 psia) of 0.1298 g/mL. An average length of the fibers was0.891 mm and an average width of the fibers was 0.026 mm, giving anaverage L/D of 34:1. A scanning electron micrograph of the fibrousmaterial is shown in FIG. 28 at 25× magnification.

Example 4 Preparation of Thrice Sheared Fibrous Material from BleachedKraft Board

A 1500 pound skid of virgin bleached white Kraft board having a bulkdensity of 30 lb/ft³ was obtained from International Paper. The materialwas folded flat, and then fed into a 3 hp Flinch Baugh shredder at arate of approximately 15 to 20 pounds per hour. The shredder wasequipped with two 12 inch rotary blades, two fixed blades and a 0.30inch discharge screen. The gap between the rotary and fixed blades wasadjusted to 0.10 inch. The output from the shredder resembled confetti(as above). The confetti-like material was fed to a Munson rotary knifecutter, Model SC30. The discharge screen had ⅛ inch openings. The gapbetween the rotary and fixed blades was set to approximately 0.020 inch.The rotary knife cutter sheared the confetti-like pieces across theknife-edges. The material resulting from the first shearing was fed backinto the same setup and the screen was replaced with a 1/16 inch screen.This material was sheared. The material resulting from the secondshearing was fed back into the same setup and the screen was replacedwith a 1/32 inch screen. This material was sheared. The resultingfibrous material had a BET surface area of 1.6897 m²/g+/−0.0155 m²/g, aporosity of 87.7163 percent and a bulk density (@0.53 psia) of 0.1448g/mL. An average length of the fibers was 0.824 mm and an average widthof the fibers was 0.0262 mm, giving an average L/D of 32:1. A scanningelectron micrograph of the fibrous material is shown in FIG. 29 at 25×magnification.

Example 5 Preparation of Densified Fibrous Material from Bleached KraftBoard without Added Binder

Fibrous material was prepared according to Example 2. Approximately 1 lbof water was sprayed onto each 10 lb of fibrous material. The fibrousmaterial was densified using a California Pellet Mill 1100 operating at75° C. Pellets were obtained having a bulk density ranging from about 7lb/ft³ to about 15 lb/ft³.

Example 6 Preparation of Densified Fibrous Material from Bleached KraftBoard with Binder

Fibrous material was prepared according to Example 2.

A 2 weight percent stock solution of POLYOX™ WSR N10 (polyethyleneoxide) was prepared in water.

Approximately 1 lb of the stock solution was sprayed onto each 10 lb offibrous material. The fibrous material was densified using a CaliforniaPellet Mill 1100 operating at 75° C. Pellets were obtained having a bulkdensity ranging from about 15 lb/ft³ to about 40 lb/ft³.

Example 7 Reducing the Molecular Weight of Cellulose in Fibrous KraftPaper by Gamma Radiation with Minimum Oxidation

Fibrous material is prepared according to Example 4. The fibrous Kraftpaper is densified according to Example 5.

The densified pellets are placed in a glass ampoule having a maximumcapacity of 250 mL. The glass ampoule is evacuated under high vacuum(10⁻⁵ torr) for 30 minutes, and then back-filled with argon gas. Theampoule is sealed under argon. The pellets in the ampoule are irradiatedwith gamma radiation for about 3 hours at a dose rate of about 1 Mradper hour to provide an irradiated material in which the cellulose has alower molecular weight than the fibrous Kraft starting material.

Example 8 Reducing the Molecular Weight of Cellulose in Fibrous KraftPaper in Gamma Radiation with Maximum Oxidation

Fibrous material is prepared according to Example 4. The fibrous Kraftpaper is densified according to Example 5.

The densified pellets are placed in a glass ampoule having a maximumcapacity of 250 mL. The glass ampoule is sealed under an atmosphere ofair. The pellets in the ampoule are irradiated with gamma radiation forabout 3 hours at a dose rate of about 1 Mrad per hour to provide anirradiated material in which the cellulose has a lower molecular weightthan the fibrous Kraft starting material.

Example 9 Methods of Determining Molecular Weight of Cellulosic andLignocellulosic Materials by Gel Permeation Chromatography

Cellulosic and lignocellulosic materials for analysis were treatedaccording to Example 4. Sample materials presented in the followingtables include Kraft paper (P), wheat straw (WS), alfalfa (A), andswitchgrass (SG). The number “132” of the Sample ID refers to theparticle size of the material after shearing through a 1/32 inch screen.The number after the dash refers to the dosage of radiation (MRad) and“US” refers to ultrasonic treatment. For example, a sample ID “P132-10”refers to Kraft paper that has been sheared to a particle size of 132mesh and has been irradiated with 10 MRad.

TABLE 1 Peak Average Molecular Weight of Irradiated Kraft Paper SampleDosage¹ Average MW ± Source Sample ID (MRad) Ultrasound² Std Dev. KraftPaper P132 0 No 32853 ± 10006 P132-10 10 ″  61398 ± 2468** P132-100 100″ 8444 ± 580  P132-181 181 ″ 6668 ± 77  P132-US 0 Yes 3095 ± 1013 **Lowdoses of radiation appear to increase the molecular weight of somematerials ¹Dosage Rate = 1 MRad/hour ²Treatment for 30 minutes with 20kHz ultrasound using a 1000 W horn under re-circulating conditions withthe material dispersed in water.

TABLE 2 Peak Average Molecular Weight of Irradiated Materials PeakDosage¹ Average MW ± Sample ID # (MRad) Ultrasound² Std Dev. WS132 1 0No 1407411 ± 175191 2 ″ ″ 39145 ± 3425 3 ″ ″ 2886 ± 177 WS132-10* 1 10 ″26040 ± 3240 WS132-100* 1 100 ″ 23620 ± 453  A132 1 0 ″ 1604886 ± 1517012 ″ ″ 37525 ± 3751 3 ″ ″ 2853 ± 490 A132-10* 1 10 ″ 50853 ± 1665 2 ″ ″2461 ± 17  A132-100* 1 100 ″ 38291 ± 2235 2 ″ ″ 2487 ± 15  SG132 1 0 ″1557360 ± 83693  2 ″ ″ 42594 ± 4414 3 ″ ″ 3268 ± 249 SG132-10* 1 10 ″60888 ± 9131 SG132-100* 1 100 ″ 22345 ± 3797 SG132-10-US 1 10 Yes  86086± 43518 2 ″ ″ 2247 ± 468 SG132-100-US 1 100 ″  4696 ± 1465 *Peakscoalesce after treatment **Low doses of radiation appear to increase themolecular weight of some materials ¹Dosage Rate = 1 MRad/hour ²Treatmentfor 30 minutes with 20 kHz ultrasound using a 1000 W horn underre-circulating conditions with the material dispersed in water.

Gel Permeation Chromatography (GPC) is used to determine the molecularweight distribution of polymers. During GPC analysis, a solution of thepolymer sample is passed through a column packed with a porous geltrapping small molecules. The sample is separated based on molecularsize with larger molecules eluting sooner than smaller molecules. Theretention time of each component is most often detected by refractiveindex (RI), evaporative light scattering (ELS), or ultraviolet (UV) andcompared to a calibration curve. The resulting data is then used tocalculate the molecular weight distribution for the sample.

A distribution of molecular weights rather than a unique molecularweight is used to characterize synthetic polymers. To characterize thisdistribution, statistical averages are utilized. The most common ofthese averages are the “number average molecular weight” (M_(n)) and the“weight average molecular weight” (M_(w)).

M_(n) is similar to the standard arithmetic mean associated with a groupof numbers. When applied to polymers, M_(n) refers to the averagemolecular weight of the molecules in the polymer. M_(n) is calculatedaffording the same amount of significance to each molecule regardless ofits individual molecular weight. The average M_(n) is calculated by thefollowing formula where N_(i) is the number of molecules with a molarmass equal to M_(i).

${\overset{\_}{M}}_{n} = \frac{\sum\limits_{i}{N_{i}M_{i}}}{\sum\limits_{i}N_{i}}$

M_(w) is another statistical descriptor of the molecular weightdistribution that places a greater emphasis on larger molecules thansmaller molecules in the distribution. The formula below shows thestatistical calculation of the weight average molecular weight.

${\overset{\_}{M}}_{w} = \frac{\sum\limits_{i}{N_{i}M_{i}^{2}}}{\sum\limits_{i}{N_{i}M_{i}}}$

The polydispersity index or PI is defined as the ratio of M_(w)/M_(n).The larger the PI, the broader or more disperse the distribution. Thelowest value that a PI can be is 1. This represents a monodispersesample; that is, a polymer with all of the molecules in the distributionbeing the same molecular weight.

The peak molecular weight value (M_(p)) is another descriptor defined asthe mode of the molecular weight distribution. It signifies themolecular weight that is most abundant in the distribution. This valuealso gives insight to the molecular weight distribution.

Most GPC measurements are made relative to a different polymer standard.The accuracy of the results depends on how closely the characteristicsof the polymer being analyzed match those of the standard used. Theexpected error in reproducibility between different series ofdeterminations, calibrated separately, is ca. 5-10% and ischaracteristic to the limited precision of GPC determinations.Therefore, GPC results are most useful when a comparison between themolecular weight distributions of different samples is made during thesame series of determinations.

The lignocellulosic samples required sample preparation prior to GPCanalysis. First, a saturated solution (8.4% by weight) of lithiumchloride (LiCl) was prepared in dimethyl acetamide (DMAc). Approximately100 mg of the sample was added to approximately 10 g of a freshlyprepared saturated LiCl/DMAc solution, and the mixture was heated toapproximately 150° C.-170° C. with stirring for 1 hour. The resultingsolutions were generally light-to dark-yellow in color. The temperaturesof the solutions were decreased to approximately 100° C. and heated foran additional 2 hours. The temperature of the solutions were thendecreased to approximately 50° C. and the sample solution was heated forapproximately 48 to 60 hours. Of note, samples irradiated at 100 MRadwere more easily solubilized as compared to their untreated counterpart.Additionally, the sheared samples (denoted by the number 132) hadslightly lower average molecular weights as compared with uncut samples.

The resulting sample solutions were diluted 1:1 using DMAc as solventand were filtered through a 0.45 μm PTFE filter. The filtered samplesolutions were then analyzed by GPC. The peak average molecular weight(Mp) of the samples, as determined by Gel Permeation Chromatography(GPC), are summarized in Tables 1 and 2. Each sample was prepared induplicate and each preparation of the sample was analyzed in duplicate(two injections) for a total of four injections per sample. The EasiCalpolystyrene standards PS1A and PS1B were used to generate a calibrationcurve for the molecular weight scale from about 580 to 7,500,00 Daltons.

TABLE 3 GPC Analysis Conditions Instrument: Waters Alliance GPC 2000Plgel 10μ Mixed-B Columns (3): S/N's: 10M-MB-148-83; 10M-MB-148-84;10M-MB-174-129 Mobile Phase (solvent): 0.5% LiCl in DMAc (1.0 mL/min.)Column/Detector Temperature: 70° C. Injector Temperature: 70° C. SampleLoop Size: 323.5 μL

Example 10 Determining Crystallinity of Irradiated Material by X-RayDiffraction

X-ray diffraction (XRD) is a method by which a crystalline sample isirradiated with monoenergetic x-rays. The interaction of the latticestructure of the sample with these x-rays is recorded and providesinformation about the crystalline structure being irradiated. Theresulting characteristic “fingerprint” allows for the identification ofthe crystalline compounds present in the sample. Using a whole-patternfitting analysis (the Rietvelt Refinement), it is possible to performquantitative analyses on samples containing more than one crystallinecompound.

TABLE 4 XRD Data Including Domain Size and % Crystallinity Domain SizeSample ID (Å) % Crystallinity P132 55 55 P132-10 46 58 P132-100 50 55P132-181 48 52 P132-US 26 40 A132 28 42 A132-10 26 40 A132-100 28 35WS132 30 36 WS132-10 27 37 WS132-100 30 41 SG132 29 40 SG132-10 28 38SG132-100 28 37 SG132-10-US 25 42 SG132-100-US 21 34

Each sample was placed on a zero background holder and placed in aPhillips PW1800 diffractometer using Cu radiation. Scans were then runover the range of 5° to 50° with a step size of 0.05° and a countingtime of 2 hours each.

Once the diffraction patterns were obtained, the phases were identifiedwith the aid of the Powder Diffraction File published by theInternational Centre for Diffraction Data. In all samples thecrystalline phase identified was cellulose—Ia, which has a triclinicstructure.

The distinguishing feature among the 20 samples is the peak breadth,which is related to the crystallite domain size. The experimental peakbreadth was used to compute the domain size and percent crystallinityand are reported in Table 4.

Percent crystallinity (X_(c)%) is measured as a ratio of the crystallinearea to the total area under the x-ray diffraction peaks,

${X_{c}\mspace{14mu}\%} = {\frac{A_{C}}{\left\{ {A_{a} + A_{C}} \right\}} \times 100\%}$where,

-   -   A_(c)=Area of crystalline phase    -   A_(a)=Area of amorphous phase    -   X_(c)=Percent of crystallinity

To determine the percent crystallinity for each sample it was necessaryto first extract the amount of the amorphous phase. This is done byestimating the area of each diffraction pattern that can be attributedto the crystalline phase (represented by the sharper peaks) and thenon-crystalline phase (represented by the broad humps beneath thepattern and centered at 22° and 38°.

A systematic process was used to minimize error in these calculationsdue to broad crystalline peaks as well as high background intensity.First, a linear background was applied and then removed. Second, twoGaussian peaks centered at 22° and 38° with widths of 10-12° each werefitted to the humps beneath the crystalline peaks. Third, the areabeneath the two broad Gaussian peaks and the rest of the pattern weredetermined. Finally, percent crystallinity was calculated by dividingthe area beneath the crystalline peak by the total intensity (afterbackground subtraction). Domain size and % crystallinity of the samplesas determined by X-ray diffraction (XRD) are presented in Table 4.

Example 11 Porosimetry Analysis of Irradiated Materials

Mercury pore size and pore volume analysis (Table 5) is based on forcingmercury (a non-wetting liquid) into a porous structure under tightlycontrolled pressures. Since mercury does not wet most substances andwill not spontaneously penetrate pores by capillary action, it must beforced into the voids of the sample by applying external pressure. Thepressure required to fill the voids is inversely proportional to thesize of the pores. Only a small amount of force or pressure is requiredto fill large voids, whereas much greater pressure is required to fillvoids of very small pores.

TABLE 5 Pore Size and Volume Distribution by Mercury Porosimetry TotalTotal Median Pore Median Pore Average Pore Bulk Density ApparentIntrusion Pore Diameter Diameter Diameter @ 0.50 (skeletal) Volume Area(Volume) (Area) (4V/A) psia Density Porosity Sample ID (mL/g) (m²/g)(μm) (μm) (μm) (g/mL) (g/mL) (%) P132 6.0594 1.228 36.2250 13.727819.7415 0.1448 1.1785 87.7163 P132-10 5.5436 1.211 46.3463 4.564618.3106 0.1614 1.5355 89.4875 P132-100 5.3985 0.998 34.5235 18.200521.6422 0.1612 1.2413 87.0151 P132-181 3.2866 0.868 25.3448 12.241015.1509 0.2497 1.3916 82.0577 P132-US 6.0005 14.787 98.3459 0.00551.6231 0.1404 0.8894 84.2199 A132 2.0037 11.759 64.6308 0.0113 0.68160.3683 1.4058 73.7990 A132-10 1.9514 10.326 53.2706 0.0105 0.7560 0.37681.4231 73.5241 A132-100 1.9394 10.205 43.8966 0.0118 0.7602 0.37601.3889 72.9264 SG132 2.5267 8.265 57.6958 0.0141 1.2229 0.3119 1.470878.7961 SG132-10 2.1414 8.643 26.4666 0.0103 0.9910 0.3457 1.331574.0340 SG132-100 2.5142 10.766 32.7118 0.0098 0.9342 0.3077 1.359077.3593 SG132-10-US 4.4043 1.722 71.5734 1.1016 10.2319 0.1930 1.288385.0169 SG132-100-US 4.9665 7.358 24.8462 0.0089 2.6998 0.1695 1.073184.2010 WS132 2.9920 5.447 76.3675 0.0516 2.1971 0.2773 1.6279 82.9664WS132-10 3.1138 2.901 57.4727 0.3630 4.2940 0.2763 1.9808 86.0484WS132-100 3.2077 3.114 52.3284 0.2876 4.1199 0.2599 1.5611 83.3538

The AutoPore 9520 can attain a maximum pressure of 414 MPa or 60,000psia. There are four low pressure stations for sample preparation andcollection of macropore data from 0.2 psia to 50 psia. There are twohigh pressure chambers which collects data from 25 psia to 60,000 psia.The sample is placed in a bowl-like apparatus called a penetrometer,which is bonded to a glass capillary stem with a metal coating. Asmercury invades the voids in and around the sample, it moves down thecapillary stem. The loss of mercury from the capillary stem results in achange in the electrical capacitance. The change in capacitance duringthe experiment is converted to volume of mercury by knowing the stemvolume of the penetrometer in use. A variety of penetrometers withdifferent bowl (sample) sizes and capillaries are available toaccommodate most sample sizes and configurations. Table 6 below definessome of the key parameters calculated for each sample.

TABLE 6 Definition of Parameters Parameter Description Total IntrusionThe total volume of mercury intruded during an Volume: experiment. Thiscan include interstitial filling between small particles, porosity ofsample, and compression volume of sample. Total Pore Area: The totalintrusion volume converted to an area assuming cylindrical shaped pores.Median Pore Diameter The size at the 50^(th) percentile on thecumulative (volume): volume graph. Median Pore Diameter The size at the50^(th) percentile on the cumulative (area): area graph. Average PoreThe total pore volume divided by the total pore Diameter: area (4V/A).Bulk Density: The mass of the sample divided by the bulk volume. Bulkvolume is determined at the filling pressure, typically 0.5 psia.Apparent Density: The mass of sample divided by the volume of samplemeasured at highest pressure, typically 60,000 psia. Porosity: (BulkDensity/Apparent Density) × 100%

Example 12 Particle Size Analysis of Irradiated Materials

The technique of particle sizing by static light scattering is based onMie theory (which also encompasses Fraunhofer theory). Mie theorypredicts the intensity vs. angle relationship as a function of the sizefor spherical scattering particles provided that other system variablesare known and held constant. These variables are the wavelength ofincident light and the relative refractive index of the sample material.Application of Mie theory provides the detailed particle sizeinformation. Table 7 summarizes particle size using median diameter,mean diameter, and modal diameter as parameters.

TABLE 7 Particle Size by Laser Light Scattering (Dry Sample Dispersion)Median Diameter Mean Diameter Modal Diameter Sample ID (μm) (μm) (μm)A132 380.695 418.778 442.258 A132-10 321.742 366.231 410.156 A132-100301.786 348.633 444.169 SG132 369.400 411.790 455.508 SG132-10 278.793325.497 426.717 SG132-100 242.757 298.686 390.097 WS132 407.335 445.618467.978 WS132-10 194.237 226.604 297.941 WS132-100 201.975 236.037307.304

Particle size was determined by Laser Light Scattering (Dry SampleDispersion) using a Malvern Mastersizer 2000 using the followingconditions:

Feed Rate: 35% Disperser Pressure: 4 Bar Optical Model: (2.610, 1.000i),1.000

An appropriate amount of sample was introduced onto a vibratory tray.The feed rate and air pressure were adjusted to ensure that theparticles were properly dispersed. The key component is selecting an airpressure that will break up agglomerations, but does not compromise thesample integrity. The amount of sample needed varies depending on thesize of the particles. In general, samples with fine particles requireless material than samples with coarse particles.

Example 13 Surface Area Analysis of Irradiated Materials

Surface area of each sample was analyzed using a Micromeritics ASAP 2420Accelerated Surface Area and Porosimetry System. The samples wereprepared by first degassing for 16 hours at 40° C. Next, free space(both warm and cold) with helium is calculated and then the sample tubeis evacuated again to remove the helium. Data collection begins afterthis second evacuation and consists of defining target pressures whichcontrols how much gas is dosed onto the sample. At each target pressure,the quantity of gas adsorbed and the actual pressure are determined andrecorded. The pressure inside the sample tube is measured with apressure transducer. Additional doses of gas will continue until thetarget pressure is achieved and allowed to equilibrate. The quantity ofgas adsorbed is determined by summing multiple doses onto the sample.The pressure and quantity define a gas adsorption isotherm and are usedto calculate a number of parameters, including BET surface area (Table8).

TABLE 8 Summary of Surface Area by Gas Adsorption BET Surface Sample IDSingle point surface area (m²/g) Area (m²/g) P132 @ P/Po = 0.2503877711.5253 1.6897 P132-10 @ P/Po = 0.239496722 1.0212 1.2782 P132-100 @ P/Po= 0.240538100 1.0338 1.2622 P132-181 @ P/Po = 0.239166091 0.5102 0.6448P132-US @ P/Po = 0.217359072 1.0983 1.6793 A132 @ P/Po = 0.2400406100.5400 0.7614 A132-10 @ P/Po = 0.211218936 0.5383 0.7212 A132-100 @ P/Po= 0.238791097 0.4258 0.5538 SG132 @ P/Po = 0.237989353 0.6359 0.8350SG132-10 @ P/Po = 0.238576905 0.6794 0.8689 SG132-100 @ P/Po =0.241960361 0.5518 0.7034 SG132-10-US @ P/Po = 0.225692889 0.5693 0.7510SG132-100-US @ P/Po = 0.225935246 1.0983 1.4963 WS132 @ P/Po =0.237823664 0.6582 0.8663 WS132-10 @ P/Po = 0.238612476 0.6191 0.7912WS132-100 @ P/Po = 0.238398832 0.6255 0.8143

The BET model for isotherms is a widely used theory for calculating thespecific surface area. The analysis involves determining the monolayercapacity of the sample surface by calculating the amount required tocover the entire surface with a single densely packed layer of krypton.The monolayer capacity is multiplied by the cross sectional area of amolecule of probe gas to determine the total surface area. Specificsurface area is the surface area of the sample aliquot divided by themass of the sample.

Example 14 Fiber Length Determination of Irradiated Materials

Fiber length distribution testing was performed in triplicate on thesamples submitted using the Techpap MorFi LB01 system. The averagelength and width are reported in Table 9.

TABLE 9 Summary of Lignocellulosic Fiber Length and Width Data AverageStatistically Arithmetic Length Corrected Average Average Weighted inLength Weighted Width Sample ID (mm) Length (mm) in Length (mm) (μm)P132-10 0.484 0.615 0.773 24.7 P132-100 0.369 0.423 0.496 23.8 P132-1810.312 0.342 0.392 24.4 A132-10 0.382 0.423 0.650 43.2 A132-100 0.3620.435 0.592 29.9 SG132-10 0.328 0.363 0.521 44.0 SG132-100 0.325 0.3510.466 43.8 WS132-10 0.353 0.381 0.565 44.7 WS132-100 0.354 0.371 0.53645.4

Example 15 Ultrasonic Treatment of Irradiated and Un-irradiatedSwitchgrass

Switchgrass was sheared according to Example 4. The switchgrass wastreated by ultrasound alone or irradiation with 10 Mrad or 100 Mrad ofgamma rays, and then sonicated. The resulting materials correspond toG132-BR (un-irradiated), G132-10-BR (10 Mrad and sonication) andG132-100-BR (100 Mrad and sonication), as presented in Table 1.Sonication was performed on each sample for 30 minutes using 20 kHzultrasound from a 1000 W horn under re-circulating conditions. Eachsample was dispersed in water at a concentration of about 0.10 g/mL.

FIGS. 30 and 31 show the apparatus used for sonication. Apparatus 500includes a converter 502 connected to booster 504 communicating with ahorn 506 fabricated from titanium or an alloy of titanium. The horn,which has a seal 510 made from VITON® fluoroelastomer about itsperimeter on its processing side, forms a liquid tight seal with aprocessing cell 508. The processing side of the horn is immersed in aliquid, such as water, that has dispersed therein the sample to besonicated. Pressure in the cell is monitored with a pressure gauge 512.In operation, each sample is moved by pump 517 from tank 516 through theprocessing cell and is sonicated. After, sonication, the sample iscaptured in tank 520. The process can be reversed in that the contentsof tank 520 can be sent through the processing cell and captured in tank516. This process can be repeated a number of times until a desiredlevel of processing is delivered to the sample.

Example 16 Scanning Electron Micrographs of Un-Irradiated Switchgrass inComparison to Irradiated and Irradiated and Sonicated Switchgrass

Switchgrass samples for the scanning electron micrographs were appliedto carbon tape and gold sputter coated (70 seconds). Images were takenwith a JEOL 6500 field emission scanning electron microscope.

FIG. 32 is a scanning electron micrograph at 1000× magnification of afibrous material produced from shearing switchgrass on a rotary knifecutter, and then passing the sheared material through a 1/32 inchscreen.

FIGS. 33 and 34 are scanning electron micrographs of the fibrousmaterial of FIG. 32 after irradiation with 10 Mrad and 100 Mrad gammarays, respectively, at 1000× magnification.

FIG. 35 is a scanning electron micrographs of the fibrous material ofFIG. 32 after irradiation with 10 Mrad and sonication at 1000×magnification.

FIG. 36 is a scanning electron micrographs of the fibrous material ofFIG. 32 after irradiation with 100 Mrad and sonication at 1000×magnification.

Example 17 Infrared Spectrum of Irradiated Kraft Paper in Comparison toUn-Irradiated Kraft Paper

The FT-IR analysis was performed on a Nicolet/Impact 400. The resultsindicate that all samples reported in Table 1 are consistent with acellulose-based material.

FIG. 37 is an infrared spectrum of Kraft board paper sheared accordingto Example 4, while FIG. 38 is an infrared spectrum of the Kraft paperof FIG. 38 after irradiation with 100 Mrad of gamma radiation. Theirradiated sample shows an additional peak in region A (centered about1730 cm⁻¹) that is not found in the un-irradiated material.

Example 18 Combination of Electron Beam and Sonication Pretreatment

Switchgrass is used as the feedstock and is sheared with a Munson rotaryknife cutter into a fibrous material. The fibrous material is thenevenly distributed onto an open tray composed of tin with an area ofgreater than about 500 in². The fibrous material is distributed so thatit has a depth of about 1-2 inches in the open tray. The fibrousmaterial may be distributed in plastic bags at lower doses ofirradiation (under 10 MRad), and left uncovered on the metal tray athigher doses of radiation.

Separate samples of the fibrous material are then exposed to successivedoses of electron beam radiation to achieve a total dose of 1 Mrad, 2Mrad, 3, Mrad, 5 Mrad, 10 Mrad, 50 Mrad, and 100 Mrad. Some samples aremaintained under the same conditions as the remaining samples, but arenot irradiated, to serve as controls. After cooling, the irradiatedfibrous material is sent on for further processing through a sonicationdevice.

The sonication device includes a converter connected to boostercommunicating with a horn fabricated from titanium or an alloy oftitanium. The horn, which has a seal made from VITON® fluoroelastomerabout its perimeter on its processing side, forms a liquid tight sealwith a processing cell. The processing side of the horn is immersed in aliquid, such as water, into which the irradiated fibrous material to besonicated is immersed. Pressure in the cell is monitored with a pressuregauge. In operation, each sample is moved by pump through the processingcell and is sonicated.

To prepare the irradiated fibrous material for sonication, theirradiated fibrous material is removed from any container (e.g., plasticbags) and is dispersed in water at a concentration of about 0.10 g/mL.Sonication is performed on each sample for 30 minutes using 20 kHzultrasound from a 1000 W horn under re-circulating conditions. Aftersonication, the irradiated fibrous material is captured in a tank. Thisprocess can be repeated a number of times until a desired level ofprocessing is achieved based on monitoring the structural changes in theswitchgrass. Again, some irradiated samples are kept under the sameconditions as the remaining samples, but are not sonicated, to serve ascontrols. In addition, some samples that were not irradiated aresonicated, again to serve as controls. Thus, some controls are notprocessed, some are only irradiated, and some are only sonicated.

Example 19 Microbial Testing of Pretreated Biomass

Specific lignocellulosic materials pretreated as described herein areanalyzed for toxicity to common strains of yeast and bacteria used inthe biofuels industry for the fermentation step in ethanol production.Additionally, sugar content and compatibility with cellulase enzymes areexamined to determine the viability of the treatment process. Testing ofthe pretreated materials is carried out in two phases as follows.

I. Toxicity and Sugar Content

Toxicity of the pretreated grasses and paper feedstocks is measured inyeast Saccharomyces cerevisiae (wine yeast) and Pichia stipitis (ATCC66278) as well as the bacteria Zymomonas mobilis (ATCC 31821) andClostridium thermocellum (ATCC 31924). A growth study is performed witheach of the organisms to determine the optimal time of incubation andsampling.

Each of the feedstocks is then incubated, in duplicate, with S.cerevisiae, P. stipitis, Z. mobilis, and C. thermocellum in a standardmicrobiological medium for each organism. YM broth is used for the twoyeast strains, S. cerevisiae and P. stipitis. RM medium is used for Z.mobilis and CM4 medium for C. thermocellum. A positive control, withpure sugar added, but no feedstock, is used for comparison. During theincubation, a total of five samples is taken over a 12 hour period attime 0, 3, 6, 9, and 12 hours and analyzed for viability (plate countsfor Z. mobilis and direct counts for S. cerevisiae) and ethanolconcentration.

Sugar content of the feedstocks is measured using High PerformanceLiquid Chromatography (HPLC) equipped with either a Shodex® sugar SP0810or Biorad Aminex® HPX-87P column. Each of the feedstocks (approx. 5 g)is mixed with reverse osmosis (RO) water for 1 hour. The liquid portionof the mixture is removed and analyzed for glucose, galactose, xylose,mannose, arabinose, and cellobiose content. The analysis is performedaccording to National Bioenergy Center protocol Determination ofStructural Carbohydrates and Lignin in Biomass.

II. Cellulase Compatibility

Feedstocks are tested, in duplicate, with commercially availableAccellerase® 1000 enzyme complex, which contains a complex of enzymesthat reduces lignocellulosic biomass into fermentable sugars at therecommended temperature and concentration in an Erlenmeyer flask. Theflasks are incubated with moderate shaking at around 200 rpm for 12hours. During that time, samples are taken every three hours at time 0,3, 6, 9, and 12 hours to determine the concentration of reducing sugars(Hope and Dean, Biotech J., 1974, 144:403) in the liquid portion of theflasks.

Example 20 Alcohol Production Using Irradiation-Sonication Pretreatment

The optimum size for biomass conversion plants is affected by factorsincluding economies of scale and the type and availability of biomassused as feedstock. Increasing plant size tends to increase economies ofscale associated with plant processes. However, increasing plant sizealso tends to increase the costs (e.g., transportation costs) per unitof biomass feedstock. Studies analyzing these factors suggest that theappropriate size for biomass conversion plants can range from 2000 to10,000 dried tons of biomass feedstock per day. The plant describedbelow is sized to process 2000 tons of dry biomass feedstock per day.

FIG. 39 shows a process schematic of a biomass conversion systemconfigured to process switchgrass. The feed preparation subsystemprocesses raw biomass feedstock to remove foreign objects and provideconsistently sized particles for further processing. The pretreatmentsubsystem changes the molecular structure (e.g., reduces the averagemolecular weight and the crystallinity) of the biomass feedstock byirradiating the biomass feedstock, mixing the irradiated the biomassfeedstock with water to form a slurry, and applying ultrasonic energy tothe slurry. The irradiation and sonication convert the cellulosic andlignocellulosic components of the biomass feedstock into fermentablematerials. The primary process subsystem ferments the glucose and otherlow weight sugars present after pretreatment to form alcohols.

Feed Preparation

The selected design feed rate for the plant is 2,000 dry tons per day ofswitchgrass biomass. The design feed is chopped and/or shearedswitchgrass.

Biomass feedstock in the form of bales of switchgrass are received bythe plant on truck trailers. As the trucks are received, they areweighed and unloaded by forklifts. Some bales are sent to on-sitestorage while others are taken directly to the conveyors. From there,the bales are conveyed to an automatic unwrapping system that cuts awaythe plastic wrapping and/or net surrounding the bales. The biomassfeedstock is then conveyed past a magnetic separator to remove trampmetal, after which it is introduced to shredder-shearer trains where thematerial is reduced in size. Finally, the biomass feedstock is conveyedto the pretreatment subsystem.

In some cases, the switchgrass bales are wrapped with plastic net toensure they don't break apart when handled, and may also be wrapped inplastic film to protect the bale from weather. The bales are eithersquare or round. The bales are received at the plant from off-sitestorage on large truck trailers.

Since switchgrass is only seasonally available, long-term storage isrequired to provide feed to the plant year-round. Long-term storage willlikely consist of 400-500 acres of uncovered piled rows of bales at alocation (or multiple locations) reasonably close to the ethanol plant.On-site short-term storage is provided equivalent to 72 hours ofproduction at an outside storage area. Bales and surrounding access waysas well as the transport conveyors will be on a concrete slab. Aconcrete slab is used because of the volume of traffic required todeliver the large amount of biomass feedstock required. A concrete slabwill minimize the amount of standing water in the storage area, as wellas reduce the biomass feedstock's exposure to dirt. The stored materialprovides a short-term supply for weekends, holidays, and when normaldirect delivery of material into the process is interrupted.

The bales are off-loaded by forklifts and are placed directly onto baletransport conveyors or in the short-term storage area. Bales are alsoreclaimed from short-term storage by forklifts and loaded onto the baletransport conveyors.

Bales travel to one of two bale unwrapping stations. Unwrapped bales arebroken up using a spreader bar and then discharged onto a conveyor whichpasses a magnetic separator to remove metal prior to shredding. A trampiron magnet is provided to catch stray magnetic metal and a scalpingscreen removes gross oversize and foreign material ahead of multipleshredder-shearer trains, which reduce the biomass feedstock to theproper size for pretreatment. The shredder-shearer trains includeshredders and rotary knife cutters. The shredders reduce the size of theraw biomass feedstock and feed the resulting material to the rotaryknife cutters. The rotary knife cutters concurrently shear the biomassfeedstock and screen the resulting material.

Three storage silos are provided to limit overall system downtime due torequired maintenance on and/or breakdowns of feed preparation subsystemequipment. Each silo can hold approximately 55,000 cubic feet of biomassfeedstock (˜3 hours of plant operation).

Pretreatment

A conveyor belt carries the biomass feedstock from the feed preparationsubsystem 110 to the pretreatment subsystem 114. As shown in FIG. 40, inthe pretreatment subsystem 114, the biomass feedstock is irradiatedusing electron beam emitters, mixed with water to form a slurry, andsubjected to the application of ultrasonic energy. As discussed above,irradiation of the biomass feedstock changes the molecular structure(e.g., reduces the average molecular weight and the crystallinity) ofthe biomass feedstock. Mixing the irradiated biomass feedstock into aslurry and applying ultrasonic energy to the slurry further changes themolecular structure of the biomass feedstock. Application of theradiation and sonication in sequence may have synergistic effects inthat the combination of techniques appears to achieve greater changes tothe molecular structure (e.g., reduces the average molecular weight andthe crystallinity) than either technique can efficiently achieve on itsown. Without wishing to be bound by theory, in addition to reducing thepolymerization of the biomass feedstock by breaking intramolecular bondsbetween segments of cellulosic and lignocellulosic components of thebiomass feedstock, the irradiation may make the overall physicalstructure of the biomass feedstock more brittle. After the brittlebiomass feedstock is mixed into a slurry, the application of ultrasonicenergy further changes the molecular structure (e.g., reduces theaverage molecular weight and the crystallinity) and also can reduce thesize of biomass feedstock particles.

Electron Beam Irradiation

The conveyor belt 491 carrying the biomass feedstock into thepretreatment subsystem distributes the biomass feedstock into multiplefeed streams (e.g., 50 feed streams) each leading to separate electronbeam emitters 492. In this embodiment, the biomass feedstock isirradiated while it is dry. Each feed stream is carried on a separateconveyor belt to an associated electron beam emitter. Each irradiationfeed conveyor belt can be approximately one meter wide. Before reachingthe electron beam emitter, a localized vibration is induced in eachconveyor belt to evenly distribute the dry biomass feedstock over thecross-sectional width of the conveyor belt.

Electron beam emitter 492 (e.g., electron beam irradiation devicescommercially available from Titan Corporation, San Diego, Calif.) areconfigured to apply a 100 kilo-Gray dose of electrons applied at a powerof 300 kW. The electron beam emitters are scanning beam devices with asweep width of 1 meter to correspond to the width of the conveyor belt.In some embodiments, electron beam emitters with large, fixed beamwidths are used. Factors including belt/beam width, desired dose,biomass feedstock density, and power applied govern the number ofelectron beam emitters required for the plant to process 2,000 tons perday of dry feed.

Sonication

The irradiated biomass feedstock is mixed with water to form a slurrybefore ultrasonic energy is applied. There can be a separate sonicationsystem associated with each electron beam feed stream or severalelectron beam streams can be aggregated as feed for a single sonicationsystem.

In each sonication system, the irradiated biomass feedstock is fed intoa reservoir 1214 through a first intake 1232 and water is fed into thereservoir 1214 through second intake 1234. Appropriate valves (manual orautomated) control the flow of biomass feedstock and the flow of waterto produce a desired ratio of biomass feedstock to water (e.g., 10%cellulosic material, weight by volume). Each reservoir 1214 includes amixer 1240 to agitate the contents of volume 1236 and disperse biomassfeedstock throughout the water.

In each sonication system, the slurry is pumped (e.g., using a recessedimpeller vortex pump 1218) from reservoir 1214 to and through a flowcell 1224 including an ultrasonic transducer 1226. In some embodiments,pump 1218 is configured to agitate the slurry 1216 such that the mixtureof biomass feedstock and water is substantially uniform at inlet 1220 ofthe flow cell 1224. For example, the pump 1218 can agitate the slurry1216 to create a turbulent flow that persists throughout the pipingbetween the first pump and inlet 1220 of flow cell 1224.

Within the flow cell 1224, ultrasonic transducer 1226 transmitsultrasonic energy into slurry 1216 as the slurry flows through flow cell1224. Ultrasonic transducer 1226 converts electrical energy into highfrequency mechanical energy (e.g., ultrasonic energy) which is thendelivered to the slurry through booster 48. Ultrasonic transducers arecommercially available (e.g., from Hielscher USA, Inc. of Ringwood,N.J.) that are capable of delivering a continuous power of 16 kilowatts.

The ultrasonic energy traveling through booster 1248 in reactor volume1244 creates a series of compressions and rarefactions in process stream1216 with an intensity sufficient to create cavitation in process stream1216. Cavitation disaggregates components of the biomass feedstockincluding, for example, cellulosic and lignocellulosic materialdispersed in process stream 1216 (e.g., slurry). Cavitation alsoproduces free radicals in the water of process stream 1216 (e.g.,slurry). These free radicals act to further break down the cellulosicmaterial in process stream 1216. In general, about 250 MJ/m³ ofultrasonic energy is applied to process stream 1216 containing fragmentsof poplar chips. Other levels of ultrasonic energy (between about 5 andabout 4000 MJ/m³, e.g., 10, 25, 50, 100, 250, 500, 750, 1000, 2000, or3000) can be applied to other biomass feedstocks After exposure toultrasonic energy in reactor volume 1244, process stream 1216 exits flowcell 24 through outlet 1222.

Flow cell 1224 also includes a heat exchanger 1246 in thermalcommunication with at least a portion of reactor volume 1244. Coolingfluid 1248 (e.g., water) flows into heat exchanger 1246 and absorbs heatgenerated when process stream 1216 (e.g., slurry) is sonicated inreactor volume 1244. In some embodiments, the flow of cooling fluid 1248into heat exchanger 1246 is controlled to maintain an approximatelyconstant temperature in reactor volume 1244. In addition or in thealternative, the temperature of cooling fluid 1248 flowing into heatexchanger 1246 is controlled to maintain an approximately constanttemperature in reactor volume 1244.

The outlet 1242 of flow cell 1224 is arranged near the bottom ofreservoir 1214 to induce a gravity feed of process stream 1216 (e.g.,slurry) out of reservoir 1214 towards the inlet of a second pump 1230which pumps process stream 1216 (e.g., slurry) towards the primaryprocess subsystem.

Sonication systems can include a single flow path (as described above)or multiple parallel flow paths each with an associated individualsonication units. Multiple sonication units can also be arranged toseries to increase the amount of sonic energy applied to the slurry.

Primary Processes

A vacuum rotary drum type filter removes solids from the slurry beforefermentation. Liquid from the filter is pumped cooled prior to enteringthe fermentors. Filtered solids are passed to passed to thepost-processing subsystem for further processing.

The fermentation tanks are large, low pressure, stainless steel vesselswith conical bottoms and slow speed agitators. Multiple first stagefermentation tanks can be arranged in series. The temperature in thefirst stage fermentation tanks is controlled to 30 degrees centigradeusing external heat exchangers. Yeast is added to the first stagefermentation tank at the head of each series of tanks and carriesthrough to the other tanks in the series.

Second stage fermentation consists of two continuous fermentors inseries. Both fermentors are continuously agitated with slow speedmechanical mixers. Temperature is controlled with chilled water inexternal exchangers with continuous recirculation. Recirculation pumpsare of the progressive cavity type because of the high solidsconcentration.

Off gas from the fermentation tanks and fermentors is combined andwashed in a counter-current water column before being vented to theatmosphere. The off gas is washed to recover ethanol rather than for airemissions control.

Post-Processing

Distillation

Distillation and molecular sieve adsorption are used to recover ethanolfrom the raw fermentation beer and produce 99.5% ethanol. Distillationis accomplished in two columns—the first, called the beer column,removes the dissolved CO₂ and most of the water, and the secondconcentrates the ethanol to a near azeotropic composition.

All the water from the nearly azeotropic mixture is removed by vaporphase molecular sieve adsorption. Regeneration of the adsorption columnsrequires that an ethanol water mixture be recycled to distillation forrecovery.

Fermentation vents (containing mostly CO₂, but also some ethanol) aswell as the beer column vent are scrubbed in a water scrubber,recovering nearly all of the ethanol. The scrubber effluent is fed tothe first distillation column along with the fermentation beer.

The bottoms from the first distillation contain all the unconvertedinsoluble and dissolved solids. The insoluble solids are dewatered by apressure filter and sent to a combustor. The liquid from the pressurefilter that is not recycled is concentrated in a multiple effectevaporator using waste heat from the distillation. The concentratedsyrup from the evaporator is mixed with the solids being sent to thecombustor, and the evaporated condensate is used as relatively cleanrecycle water to the process.

Because the amount of stillage water that can be recycled is limited, anevaporator is included in the process. The total amount of the waterfrom the pressure filter that is directly recycled is set at 25%.Organic salts like ammonium acetate or lactate, steep liquor componentsnot utilized by the organism, or inorganic compounds in the biomass endup in this stream. Recycling too much of this material can result inlevels of ionic strength and osmotic pressures that can be detrimentalto the fermenting organism's efficiency. For the water that is notrecycled, the evaporator concentrates the dissolved solids into a syrupthat can be sent to the combustor, minimizing the load to wastewatertreatment.

Wastewater Treatment

The wastewater treatment section treats process water for reuse toreduce plant makeup water requirements. Wastewater is initially screenedto remove large particles, which are collected in a hopper and sent to alandfill. Screening is followed by anaerobic digestion and aerobicdigestion to digest organic matter in the stream. Anaerobic digestionproduces a biogas stream that is rich in methane that is fed to thecombustor. Aerobic digestion produces a relatively clean water streamfor reuse in the process as well as a sludge that is primarily composedof cell mass. The sludge is also burned in the combustor. Thisscreening/anaerobic digestion/aerobic digestion scheme is standardwithin the current ethanol industry and facilities in the 1-5 milliongallons per day range can be obtained as “off-the-shelf” units fromvendors.

Combustor, Boiler, and Turbogenerator

The purpose of the combustor, boiler, and turbogenerator subsystem is toburn various by-product streams for steam and electricity generation.For example, some lignin, cellulose, and hemicellulose remainsunconverted through the pretreatment and primary processes. The majorityof wastewater from the process is concentrated to a syrup high insoluble solids. Anaerobic digestion of the remaining wastewater producesa biogas high in methane. Aerobic digestion produces a small amount ofwaste biomass (sludge). Burning these by-product streams to generatesteam and electricity allows the plant to be self sufficient in energy,reduces solid waste disposal costs, and generates additional revenuethrough sales of excess electricity.

Three primary fuel streams (post-distillate solids, biogas, andevaporator syrup) are fed to a circulating fluidized bed combustor. Thesmall amount of waste biomass (sludge) from wastewater treatment is alsosent to the combustor. A fan moves air into the combustion chamber.Treated water enters the heat exchanger circuit in the combustor and isevaporated and superheated to 510° C. (950° F.) and 86 atm (1265 psia)steam. Flue gas from the combustor preheats the entering combustion airthen enters a baghouse to remove particulates, which are landfilled. Thegas is exhausted through a stack.

A multistage turbine and generator are used to generate electricity.Steam is extracted from the turbine at three different conditions forinjection into the pretreatment reactor and heat exchange indistillation and evaporation. The remaining steam is condensed withcooling water and returned to the boiler feedwater system along withcondensate from the various heat exchangers in the process. Treated wellwater is used as makeup to replace steam used in direct injection.

Other Embodiments

A number of embodiments of the invention have been described.Nevertheless, it will be understood that various modifications may bemade without departing from the spirit and scope of the invention.

In some embodiments, relatively low doses of radiation, optionally,combined with acoustic energy, e.g., ultrasound, are utilized tocrosslink, graft, or otherwise increase the molecular weight of anatural or synthetic carbohydrate-containing material, such as any ofthose materials in any form (e.g., fibrous form) described herein, e.g.,sheared or un-sheared cellulosic or lignocellulosic materials, such ascellulose. The crosslinking, grafting, or otherwise increasing themolecular weight of the natural or synthetic carbohydrate-containingmaterial can be performed in a controlled and predetermined manner byselecting the type or types of radiation employed (e.g., e-beam andultraviolet or e-beam and gamma) and/or dose or number of doses ofradiation applied. Such a material having increased molecular weight canbe useful in making a composite, such as a fiber-resin composite, havingimproved mechanical properties, such as abrasion resistance, compressionstrength, fracture resistance, impact strength, bending strength,tensile modulus, flexural modulus and elongation at break. Crosslinking,grafting, or otherwise increasing the molecular weight of a selectedmaterial can improve the thermal stability of the material relative toan un-treated material. Increasing the thermal stability of the selectedmaterial can allow it to be processed at higher temperatures withoutdegradation. In addition, treating materials with radiation cansterilize the materials, which can reduce their tendency to rot, e.g.,while in a composite. The crosslinking, grafting, or otherwiseincreasing the molecular weight of a natural or syntheticcarbohydrate-containing material can be performed in a controlled andpredetermined manner for a particular application to provide optimalproperties, such as strength, by selecting the type or types ofradiation employed and/or dose or doses of radiation applied.

When used, the combination of radiation, e.g., low dose radiation, andacoustic energy, e.g., sonic or ultrasonic energy, can improve materialthroughput and/or minimize energy usage.

The resin can be any thermoplastic, thermoset, elastomer, adhesive, ormixtures of these resins. Suitable resins include any resin, or mixtureof resins described herein.

In addition to the resin alone, the material having the increasedmolecular weight can be combined, blended, or added to other materials,such as metals, metal alloys, ceramics (e.g., cement), lignin,elastomers, asphalts, glass, or mixtures of any of these and/or resins.When added to cement, fiber-reinforced cements can be produced havingimproved mechanical properties, such as the properties described herein,e.g., compression strength and/or fracture resistance.

Crosslinking, grafting, or otherwise increasing the molecular weight ofa natural or synthetic carbohydrate-containing material utilizingradiation can provide useful materials in many forms and for manyapplications. For example, the carbohydrate-containing material can bein the form of a paper product, such as paper, paper pulp, or papereffluent, particle board, glued lumber laminates, e.g., veneer, orplywood, lumber, e.g., pine, poplar, oak, or even balsa wood lumber.Treating paper, particle board, laminates or lumber, can increase theirmechanical properties, such as their strength. For example, treatingpine lumber with radiation can make a high strength structural material.

When paper is made using radiation, radiation can be utilized at anypoint in its manufacture. For example, the pulp can be irradiated, apressed fiber preform can be irradiated, or the finished paper itselfcan be irradiated. In some embodiments, radiation is applied at morethan one point during the manufacturing process.

For example, a fibrous material that includes a first cellulosic and/orlignocellulosic material having a first molecular weight can beirradiated in a manner to provide a second cellulosic and/orlignocellulosic material having a second molecular weight higher thanthe first molecular weight. For example, if gamma radiation is utilizedas the radiation source, a dose of from about 0.2 Mrad to about 10 Mrad,e.g., from about 0.5 Mrad to about 7.5 Mrad, or from about 2.0 Mrad toabout 5.0 Mrad, can be applied. If e-beam radiation is utilized, asmaller dose can be utilized (relative to gamma radiation), such as adose of from about 0.1 Mrad to about 5 Mrad, e.g., between about 0.2Mrad to about 3 Mrad, or between about 0.25 Mrad and about 2.5 Mrad.After the relatively low dose of radiation, the second cellulosic and/orlignocellulosic material can be combined with a material, such as aresin, and formed into a composite, e.g., by compression molding,injection molding or extrusion. Forming resin-fiber composites isdescribed in WO 2006/102543. Once composites are formed, they can beirradiated to further increase the molecular weight of thecarbohydrate-containing material while in the composite.

Alternatively, a fibrous material that includes a first cellulosicand/or lignocellulosic material having a first molecular weight can becombined with a material, such as a resin, to provide a composite, andthen the composite can be irradiated with a relatively low dose ofradiation so as to provide a second cellulosic and/or lignocellulosicmaterial having a second molecular weight higher than the firstmolecular weight. For example, if gamma radiation is utilized as theradiation source, a dose of from about 1 Mrad to about 10 Mrad can beapplied. Using this approach increases the molecular weight of thematerial while it is with a matrix, such as a resin matrix. In someembodiments, the resin is a cross-linkable resin, and, as such, itcrosslinks as the carbohydrate-containing material increases inmolecular weight, which can provide a synergistic effect to providemaximum mechanical properties to a composite. For example, suchcomposites can have excellent low temperature performance, e.g., havinga reduced tendency to break and/or crack at low temperatures, e.g.,temperatures below 0° C., e.g., below −10° C., −20° C., −40° C., −50°C., −60° C. or even below −100° C., and/or excellent performance at hightemperatures, e.g., capable of maintaining their advantageous mechanicalproperties at relatively high temperature, e.g., at temperatures above100° C., e.g., above 125° C., 150° C., 200° C., 250° C., 300° C., 400°C., or even above 500° C. In addition, such composites can haveexcellent chemical resistance, e.g., resistance to swelling in asolvent, e.g., a hydrocarbon solvent, resistance to chemical attack,e.g., by strong acids, strong bases, strong oxidants (e.g., chlorine orbleach) or reducing agents (e.g., active metals such as sodium andpotassium).

In some embodiments, the resin, or other matrix material, does notcrosslink during irradiation. In some embodiments, additional radiationis applied while the carbohydrate-containing material is within thematrix to further increase the molecular weight of thecarbohydrate-containing material. In some embodiments, the radiationcauses bonds to form between the matrix and the carbohydrate-containingmaterial.

In some embodiments, the carbohydrate-containing material is in the formof fibers. In such embodiments, when the fibers are utilized in acomposite, the fibers can be randomly oriented within the matrix. Inother embodiments, the fibers can be substantially oriented, such as inone, two, three or four directions. If desired, the fibers can becontinuous or discrete.

Any of the following additives can added to the fibrous materials,densified fibrous materials a or any other materials and compositesdescribed herein. Additives, e.g., in the form of a solid, a liquid or agas, can be added, e.g., to the combination of a fibrous material andresin. Additives include fillers such as calcium carbonate, graphite,wollastonite, mica, glass, fiber glass, silica, and talc; inorganicflame retardants such as alumina trihydrate or magnesium hydroxide;organic flame retardants such as chlorinated or brominated organiccompounds; ground construction waste; ground tire rubber; carbon fibers;or metal fibers or powders (e.g., aluminum, stainless steel). Theseadditives can reinforce, extend, or change electrical, mechanical orcompatibility properties. Other additives include lignin, fragrances,coupling agents, compatibilizers, e.g., maleated polypropylene,processing aids, lubricants, e.g., fluorinated polyethylene,plasticizers, antioxidants, opacifiers, heat stabilizers, colorants,foaming agents, impact modifiers, polymers, e.g., degradable polymers,photostabilizers, biocides, antistatic agents, e.g., stearates orethoxylated fatty acid amines. Suitable antistatic compounds includeconductive carbon blacks, carbon fibers, metal fillers, cationiccompounds, e.g., quaternary ammonium compounds, e.g.,N-(3-chloro-2-hydroxypropyl)-trimethylammonium chloride, alkanolamides,and amines. Representative degradable polymers include polyhydroxyacids, e.g., polylactides, polyglycolides and copolymers of lactic acidand glycolic acid, poly(hydroxybutyric acid), poly(hydroxyvaleric acid),poly[lactide-co-(e-caprolactone)], poly[glycolide-co-(e-caprolactone)],polycarbonates, poly(amino acids), poly(hydroxyalkanoate)s,polyanhydrides, polyorthoesters and blends of these polymers.

When described additives are included, they can be present in amounts,calculated on a dry weight basis, of from below 1 percent to as high as80 percent, based on total weight of the fibrous material. Moretypically, amounts range from between about 0.5 percent to about 50percent by weight, e.g., 5 percent, 10 percent, 20 percent, 30, percentor more, e.g., 40 percent.

Any additives described herein can be encapsulated, e.g., spray dried ormicroencapsulated, e.g., to protect the additives from heat or moistureduring handling.

The fibrous materials, densified fibrous materials, resins or additivesmay be dyed. For example, the fibrous material can be dyed beforecombining with the resin and compounding to form composites. In someembodiments, this dyeing can be helpful in masking or hiding the fibrousmaterial, especially large agglomerations of the fibrous material, inmolded or extruded parts, when this is desired. Such largeagglomerations, when present in relatively high concentrations, can showup as speckles in the surfaces of the molded or extruded parts.

For example, the desired fibrous material can be dyed using an acid dye,direct dye or a reactive dye. Such dyes are available from Spectra Dyes,Kearny, N.J. or Keystone Aniline Corporation, Chicago, Ill. Specificexamples of dyes include SPECTRA™ LIGHT YELLOW 2G, SPECTRACID™ YELLOW4GL CONC 200, SPECTRANYL™ RHODAMINE 8, SPECTRANYL™ NEUTRAL RED B,SPECTRAMINE™ BENZOPERPURINE, SPECTRADIAZO™ BLACK OB, SPECTRAMINE™TURQUOISE G, and SPECTRAMINE™ GREY LVL 200%, each being available fromSpectra Dyes.

In some embodiments, resin color concentrates containing pigments areblended with dyes. When such blends are then compounded with the desiredfibrous material, the fibrous material may be dyed in-situ during thecompounding. Color concentrates are available from Clariant.

It can be advantageous to add a scent or fragrance to the fibrousmaterials, densified fibrous or composites. For example, it can beadvantageous for the composites smell and/or look like natural wood,e.g., cedarwood. For example, the fragrance, e.g., natural woodfragrance, can be compounded into the resin used to make the composite.In some implementations, the fragrance is compounded directly into theresin as an oil. For example, the oil can be compounded into the resinusing a roll mill, e.g., a Banbury® mixer or an extruder, e.g., atwin-screw extruder with counter-rotating screws. An example of aBanbury® mixer is the F-Series Banbury® mixer, manufactured by Farrel.An example of a twin-screw extruder is the WP ZSK 50 MEGAcompounder™,manufactured by Krupp Werner & Pfleiderer. After compounding, thescented resin can be added to the fibrous material and extruded ormolded. Alternatively, master batches of fragrance-filled resins areavailable commercially from International Flavors and Fragrances, underthe tradename PolyIff™ or from the RTP Company. In some embodiments, theamount of fragrance in the composite is between about 0.005% by weightand about 10% by weight, e.g., between about 0.1% and about 5% or 0.25%and about 2.5%.

Other natural wood fragrances include evergreen or redwood. Otherfragrances include peppermint, cherry, strawberry, peach, lime,spearmint, cinnamon, anise, basil, bergamot, black pepper, camphor,chamomile, citronella, eucalyptus, pine, fir, geranium, ginger,grapefruit, jasmine, juniperberry, lavender, lemon, mandarin, marjoram,musk, myrhh, orange, patchouli, rose, rosemary, sage, sandalwood, teatree, thyme, wintergreen, ylang ylang, vanilla, new car or mixtures ofthese fragrances. In some embodiments, the amount of fragrance in thefibrous material-fragrance combination is between about 0.005% by weightand about 20% by weight, e.g., between about 0.1% and about 5% or 0.25%and about 2.5%.

While fibrous materials have been described, such as cellulosic andlignocellulosic fibrous materials, other fillers may be used for makingthe composites. For example, inorganic fillers such as calcium carbonate(e.g., precipitated calcium carbonate or natural calcium carbonate),aragonite clay, orthorhombic clays, calcite clay, rhombohedral clays,kaolin, clay, bentonite clay, dicalcium phosphate, tricalcium phosphate,calcium pyrophosphate, insoluble sodium metaphosphate, precipitatedcalcium carbonate, magnesium orthophosphate, trimagnesium phosphate,hydroxyapatites, synthetic apatites, alumina, silica xerogel, metalaluminosilicate complexes, sodium aluminum silicates, zirconiumsilicate, silicon dioxide or combinations of the inorganic additives maybe used. The fillers can have, e.g., a particle size of greater than 1micron, e.g., greater than 2 micron, 5 micron, 10 micron, 25 micron oreven greater than 35 microns.

Nanometer scale fillers can also be used alone, or in combination withfibrous materials of any size and/or shape. The fillers can be in theform of, e.g., a particle, a plate or a fiber. For example, nanometersized clays, silicon and carbon nanotubes, and silicon and carbonnanowires can be used. The filler can have a transverse dimension lessthan 1000 nm, e.g., less than 900 nm, 800 nm, 750 nm, 600 nm, 500 nm,350 nm, 300 nm, 250 nm, 200 nm, less than 100 nm, or even less than 50nm.

In some embodiments, the nano-clay is a montmorillonite. Such clays areavailable from Nanocor, Inc. and Southern Clay products, and have beendescribed in U.S. Pat. Nos. 6,849,680 and 6,737,464. The clays can besurface treated before mixing into, e.g., a resin or a fibrous material.For example, the clay can be surface is treated so that its surface isionic in nature, e.g., cationic or anionic.

Aggregated or agglomerated nanometer scale fillers, or nanometer scalefillers that are assembled into supramolecular structures, e.g.,self-assembled supramolecular structures can also be used. Theaggregated or supramolecular fillers can be open or closed in structure,and can have a variety of shapes, e.g., cage, tube or spherical.

Accordingly, other embodiments are within the scope of the followingclaims.

1. A method comprising converting a treated biomass feedstock to aproduct selected from the group consisting of alcohols, organic acids,sugars, hydrocarbons, and mixtures thereof, utilizing an enzyme and/or amicroorganism, wherein the treated biomass feedstock has been preparedby irradiating a biomass feedstock with an electron beam at a dose rateof at least 1.0 Mrad/s for a time sufficient to deliver from about 10Mrad to about 150 Mrad of radiation to the biomass feedstock so as torender the irradiated biomass feedstock more susceptible to chemical,enzymatic and/or biological attack than the biomass feedstock prior toelectron beam treatment, the biomass feedstock having been physicallytreated prior to electron beam irradiation by grinding, milling orshearing.
 2. The method of claim 1 wherein the biomass feedstock has abulk density of less than about 0.5 g/cm³.
 3. The method of claim 1wherein the initial feedstock has, prior to physical treatment, a bulkdensity of greater than about 0.7 g/cm³.
 4. The method of claim 1wherein physically treating the biomass feedstock comprises reducing thesize of the initial feedstock by stone grinding, mechanical ripping ortearing, pin grinding, or air attrition milling.
 5. The method of claim1 wherein physically treating the biomass feedstock comprises shearingthe biomass feedstock.
 6. The method of claim 5 wherein the biomassfeedstock has internal fibers, and wherein the biomass feedstock hasbeen sheared to an extent that its internal fibers are substantiallyexposed.
 7. The method of claim 1 wherein the biomass feedstockcomprises a cellulosic or lignocellulosic material.
 8. The method ofclaim 1 wherein treating the biomass feedstock is conducted underconditions selected to result in a reduction of the molecular weight ofthe biomass.
 9. The method of claim 1 wherein the biomass has a BETsurface area of greater than 0.25 m²/g.
 10. The method of claim 1wherein the biomass has a length to diameter ratio of at least
 5. 11.The method of claim 1 wherein converting the treated biomass feedstockcomprises fermenting the treated biomass feedstock.
 12. The method ofclaim 1 wherein treating the biomass feedstock is performed underconditions that are selected to result in a decrease of either one orboth of an average molecular weight and average crystallinity of thebiomass or an increase in either one or both of surface area andporosity of the biomass.
 13. The method of claim 1, wherein the biomasscomprises a material selected from the group consisting of paper, paperproducts, paper waste, wood, particle board, sawdust, agriculturalwaste, sewage, silage, grasses, rice hulls, bagasse, cotton, jute, hemp,flax, bamboo, sisal, abaca, straw, corn cobs, corn stover, switchgrass,alfalfa, hay, coconut hair, seaweed, algae, and mixtures thereof. 14.The method of claim 1 wherein the biomass feedstock has a porositygreater than 70 percent.
 15. The method of claim 1 further comprisingsubjecting the treated biomass feedstock to enzymatic hydrolysis. 16.The method of claim 1 wherein irradiating is performed at a dose rate ofabout 1 Mrad/s to about 10 Mrad/s.
 17. The method of claim 1 whereinirradiating comprises applying radiation to the lignocellulosic materialwith more than one electron beam device.
 18. The method of claim 1wherein the electron beam device delivers electrons having an energy of0.3 MeV to about 2.0 MeV.
 19. The method of claim 1 wherein the electronbeam device delivers electrons having an energy of 0.7 MeV to about 1.25MeV.
 20. The method of claim 1 wherein converting comprises contactingthe irradiated material with a cellulase in an aqueous medium.
 21. Amethod comprising irradiating a biomass feedstock with an electron beamat a dose rate of at least 1.0 Mrad/s for a time sufficient to deliverfrom about 10 Mrad to about 150 Mrad of radiation to the biomassfeedstock so as to render the irradiated biomass feedstock moresusceptible to chemical, enzymatic and/or biological attack than thebiomass feedstock prior to electron beam treatment, the biomassfeedstock having been physically treated prior to electron beamirradiation by grinding, milling or shearing; and Converting theirradiated biomass feedstock to a product selected from the groupconsisting of alcohols, organic acids, sugars, hydrocarbons, andmixtures thereof, utilizing an enzyme and/or a microorganism.
 22. Themethod of claim 21 wherein irradiating is performed at a dose rate ofabout 1 Mrad/s to about 10 Mrad/s.
 23. The method of claim 21 whereinirradiating comprises applying radiation to the lignocellulosic materialwith more than one electron beam device.
 24. The method of claim 21wherein the electron beam device delivers electrons having an energy of0.3 MeV to about 2.0 MeV.
 25. The method of claim 21 wherein theelectron beam device delivers electrons having an energy of 0.7 MeV toabout 1.25 MeV.
 26. The method of claim 21 wherein converting comprisescontacting the irradiated material with a cellulase in an aqueousmedium.